Method for asymmetric synthesis

ABSTRACT

The present invention relates to a process for asymmetric synthesis in the presence of a chiral catalyst comprising at least one complex of a metal of transition group VIII with ligands capable of dimerization via noncovalent bonds, such catalysts and their use.

This application is a National Stage of PCT/EP2004/013344 filed Nov. 24,2004 which in turn claims priority from German Application 103 55 066.6filed Nov. 25, 2003.

The present invention relates to a process for asymmetric synthesis inthe presence of a chiral catalyst comprising at least one complex of ametal of transition group VIII with ligands capable of dimerization vianoncovalent bonds, such ligands and catalysts and their use.

The term asymmetric synthesis refers to reactions in which a chiralgroup is generated from a prochiral group such that the stereoisomericproducts (enantiomers or diastereomers) are formed in unequal amounts.Asymmetric synthesis has acquired tremendous importance especially inthe pharmaceutical industry, since it is frequently the case that only aparticular optically active isomer is therapeutically active. There isthus a continuing need for new methods of carrying out asymmetricsyntheses and specific catalysts having a high degree of asymmetricinduction for particular stereocenters, i.e. the synthesis should leadto the desired isomer in high optical purity and in high chemical yield.

An important class of reactions is addition onto carbon-carbon andcarbon-heteroatom multiple bonds. Addition onto the two adjacent atomsof a C═X double bond (X═C, heteroatom) is also referred to as1,2-addition. Addition reactions can also be characterized according tothe groups added on, with hydroaddition being the addition of a hydrogenatom and carboaddition being the addition of a carbon-comprisingfragment. Thus, a 1-hydro-2-carboaddition is the addition of hydrogenand a carbon-comprising group. Important representatives of thisreaction are, for example, hydroformylation, hydrocyanation andcarbonylation. A further very important addition onto carbon-carbon andcarbon-heteroatom multiple bonds is hydrogenation. There is a need forcatalysts for asymmetric addition reactions of prochiral ethylenicallyunsaturated compounds that have good catalytic activity and highstereoselectivity.

Hydroformylation or the oxo process is an important industrial processand is employed for preparing aldehydes from olefins, carbon monoxideand hydrogen. These aldehydes can, if appropriate, be hydrogenated bymeans of hydrogen in the same process to give the corresponding oxoalcohols. Asymmetric hydroformylation is an important method forsynthesizing chiral aldehydes and is of interest as a route to chiralbuilding blocks for the preparation of flavors, cosmetics, cropprotection agents and pharmaceuticals. The hydroformylation-reactionitself is strongly exothermic and generally proceeds undersuperatmospheric pressure and at elevated temperatures in the presenceof catalysts. Catalysts used are Co, Rh, Ir, Ru, Pd or Pt compounds orcomplexes which may be modified with N-, P-, As- or Sb-comprisingligands to influence the activity and/or selectivity. In thehydroformylation reaction of olefins having more than two carbon atoms,the formation of mixtures of isomeric aldehydes can occur due to thepossible addition of CO onto each of the two carbon atoms of a doublebond. In addition, double bond isomerization can result in the formationof mixtures of isomeric olefins and possibly also isomeric aldehydeswhen using olefins having at least four carbon atoms. To achieveefficient asymmetric hydroformylation, the following conditionstherefore have to be met:

1. high activity of the catalyst, 2. high selectivity in respect of thedesired aldehyde and 3. high stereoselectivity in favor of the desiredisomer.

The use of phosphorus-comprising ligands for stabilizing and/oractivating the catalyst metal in rhodium-catalyzed low-pressurehydroformylation is known. Suitable phosphorus-comprising ligands are,for example, phosphines, phosphinites, phosphonites, phosphites,phosphoramidites, phospholes and phosphabenzenes. The most wide-spreadligands at present are triarylphosphines, e.g. triphenylphosphine andsulfonated triphenylphosphine, since these have sufficient stabilityunder the reaction conditions.

It is known that the use of chelating ligands which have two groupscapable of coordination has an advantageous effect on thestereoselectivity achieved in asymmetric hydroformylation reactions.Thus, for example, M. M. H. Lambers-Verstappen and J. de Vries describethe rhodium-catalyzed hydroformylation of unsaturated nitriles in Adv.Synth. Catal. 2003, 345, No. 4, pp. 478-482, but were able to achieve asatisfactory asymmetric hydroformylation only when using asymmetricBINAPHOS ligands. Furthermore, it is known that the use of chelatingligands also has an advantageous effect on the n-selectivity achieved inhydroformylation (cf. Moulijn, van Leeuwen and van Santen, Catalysis,vol. 79, pp. 199-248, Elsevier 1993). However, a disadvantage of the useof chelating ligands is that complicated syntheses are frequentlyrequired for their preparation and/or they are obtained only in pooryields.

In J. Org. Chem. 2000, 65, pp. 6917-6921; M. Akazome et al. describe thesynthesis, solid state structure and aggregation behavior of phosphineswhich bear a 2-pyridone ring. In J. Org. Chem. 1978, 43, pp. 947-949, G.R. Newkome and D. C. Hager describe a process for preparingpyridyidiphenylphosphines. Use as ligands in transition metal catalystsis not described in these documents. U.S. Pat. Nos. 4,786,443 and4,940,787 describe processes for the carbonylation of acetylenicallyunsaturated compounds in the presence of a palladium catalyst. Ligandsused are phosphines which bear at least one hetaryl radical, e.g. anoptionally substituted pyridyl radical. The use of phosphines which haveat least one group capable of forming noncovalent bonds as ligands isnot described.

WO 80/01690 describes a rhodium catalyst comprising at least onephosphine ligand in which two aryl groups and, via an alkylene bridge, aheteroatom-comprising radical are bound to the P atom. Thisheteroatom-comprising radical can be one of a large number of differentradicals, with radicals comprising carboxamide groups being mentionedamong others. However, this document does not teach the use of ligandshaving a functional group which is capable of forming intermolecularnoncovalent bonds. Thus, the only working example involving ligandscomprising carboxamide groups concerns(N-2-pyrrolidinonylethyl)diphenylphosphine, which is not capable offorming intermolecular noncovalent bonds between the amide groups. U.S.Pat. No. 4,687,874 has a disclosure content comparable to WO 80/01690.

The unpublished German patent application P 10313319.4 describes ahydroformylation process which is suitable for the hydroformylation of1-olefins with high n-selectivity. It uses hydroformylation catalystsbased on monophosphorus ligands which are capable of formingintermolecular noncovalent bonds. Such ligands can in principle dimerizevia intermolecular noncovalent bonds and thus form pseudochelatecomplexes.

In J. Am. Chem. Soc. 2003, 125, 6608-6609, B. Breit and W. Seichedescribe the dimerization of monodentate ligands via hydrogen bonds toform bidentate donor ligands and their use in hydroformylation catalystshaving a high regioselectivity.

None of the abovementioned documents is concerned with chiral ligands orcatalysts for use in asymmetric syntheses.

EP-A-0 614 870 describes a process for preparing optically activealdehydes by hydro-formylation of prochiral 1-olefins in the presence ofa rhodium complex comprising an unsymmetrical phosphonus-comprisingligand having a 1,1′-binaphthylene backbone as hydroformylationcatalyst. The synthesis of the unsymmetrical phosphorus-comprisingligands is complicated. EP-A-0 614 901, EP-A-0 614 902, EP-A-0 614 903,EP-A-0 684 249 and DE-A-198 53 748 describe unsymmetricalphosphorus-comprising ligands having a comparable structure.

WO 93/03839 (EP-B-0 600 020) describes an optically active metal-ligandcatalyst complex comprising an optically active pnicogen compound asligand and processes for asymmetric synthesis in the presence of such acatalyst.

BRIEF SUMMARY

It is an object of the present invention to provide a process forpreparing chiral compounds with high stereoselectivity. In addition, thedesired isomer should also be obtained in high yield. A specific objectof the invention is to provide a process which is suitable for thehydrogenation of carbon-carbon and carbon-heteroatom multiple bonds withhigh stereoselectivity. A further specific object of the presentinvention is to provide a hydroformylation process which is suitable forthe hydroformylation of olefins with high stereoselectivity. Theprocesses should preferably use catalysts whose ligands can be preparedeasily and in good yields.

It has now surprisingly been found that this object is achieved by theprovision of chiral catalysts based on monopnicogen ligands ormonopseudopnicogen ligands which are capable of forming intermolecularnoncovalent bonds. Such ligands can in principle dimerize viaintermolecular noncovalent bonds and thus form pseudochelate complexes.

The present invention accordingly provides a process for preparingchiral compounds by reacting a prochiral compound comprising at leastone ethylenically unsaturated double bond with a substrate in thepresence of a chiral catalyst comprising at least one transition metalcomplex with ligands which each have a pnicogen-comprising orpseudopnicogen-comprising group and at least one functional groupcapable of forming intermolecular, noncovalent bonds, with the complexcomprising ligands dimerized via intermolecular noncovalent bonds.

In addition, the present invention provides ligands which each have onepnicogen-comprising or pseudopnicogen-comprising group and at least onefunctional group capable of forming intermolecular, noncovalent bonds,and also chiral catalysts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “pnicogen atom” refers to an atom of main group V of thePeriodic Table of the Elements. Preferred pnicogen atoms are N, P, Asand Sb, with particular preference being given to N and P. If thepnicogen atom is a nitrogen atom, this is preferably present as an imine(═N—), i.e. it has a double bond to an adjacent atom. In particular, a Patom is used as pnicogen atom.

The term “pseudopnicogen atom” refers to an atom which behaves in thesame way as a pnicogen atom. A preferred pseudopnicogen atom is thecarbene carbon atom. Correspondingly, a “pseudopnicogen-comprisinggroup” is a group which behaves the same as a pnicogen-comprising group.Preferred pseudopnicogen-comprising groups are N-heterocyclic carbenesas are described by W. A. Herrmann in Angew. Chem. 2002, 114, pp.1342-1363. The disclosure of this document is hereby fully incorporatedby reference.

For the purposes of the present invention, “chiral compounds” arecompounds having at least one center of chirality (i.e. at least oneasymmetric atom, in particular at least one asymmetric C atom or Patom), an axis of chirality, a plane of chirality or a helicalstructure.

For the purposes of the present invention, the term “chiral catalyst” isinterpreted broadly. It comprises both catalysts having at least onechiral ligand and catalysts which have intrinsically achiral ligands butdisplay center chirality, axial chirality, planar chirality or helicitydue to the arrangement of the ligands as a result of noncovalentinteractions and/or the arrangement of the ligands in complexed form.

“Achiral compounds” are compounds which are not chiral.

For the purposes of the present invention, a “prochiral compound” is acompound having at least one prochiral center. “Asymmetric synthesis”refers to a reaction in which a compound having at least one center ofchirality, an axis of chirality, a plane of chirality or a helicalstructure is produced from a compound having at least one prochiralcenter, with the stereoisomeric products being formed in unequalamounts.

“Stereoisomers” are compounds having the same constitution but adifferent arrangement of atoms in three-dimensional space.

“Enantiomers” are stereoisomers which are mirror images of one another.The “enantiomeric excess” (ee) achieved in an asymmetric synthesis isgiven by the formula: ee[%]=(R−S)/(R+S)×100. R and S are the descriptorsof the CIP system for the two enantiomers and indicate the absoluteconfiguration around an asymmetric atom. The enantiomerically purecompound (ee=100%) is also referred to as a “homochiral compound”.

The process of the invention leads to products which are enriched in aparticular stereoisomer. The “enantiomeric excess” (ee) achieved isgenerally at least 20%, preferably at least 50%, in particular at least80%.

“Diastereomers” are stereoisomers which are not enantiomers of oneanother.

It has surprisingly been found that chiral catalysts which comprise atleast one complex with monopnicogen ligands or monopseudopnicogenligands (ligands which have only one pnicogen-comprising group orpseudopnicogen-comprising group per molecule) and are capable offorming, via intermolecular noncovalent bonds, dimers in which thedistance between the two pnicogen atoms/pseudopnicogen atoms is in arange usual for chelating ligands achieve a stereoselectivity inasymmetric synthesis which is as high as that which is otherwiseachieved only when using chelating ligands. In addition, theregioselectivity typical of chelating ligands can generally also beachieved when using these catalysts. Thus, for example, when they areused in hydroformylation, they can achieve n-selectivities of a levelwhich is otherwise achieved only when using chelating ligands.

Ligands which are capable of forming dimers via intermolecular,noncovalent bonds are also referred to as pseudochelating ligands forthe purposes of the present invention.

According to the invention, ligands which have a functional groupcapable of forming intermolecular, noncovalent bonds are used. Thesebonds are preferably hydrogen bonds or ionic bonds, in particularhydrogen bonds. In a preferred embodiment, the functional groups can begroups capable of tautomerism. The functional groups capable of formingintermolecular noncovalent bonds make the ligands capable ofassociation, i.e. formation of aggregates in the form of dimers.

For the purposes of the present invention, a pair of functional groupsof two ligands which are capable of forming intermolecular noncovalentbonds are referred to as “complementary functional groups”.“Complementary compounds” are ligand/ligand pairs which have functionalgroups which are complementary to one another. Such pairs are capable ofassociation, i.e. formation of aggregates.

The functional groups capable of forming intermolecular noncovalentbonds are preferably selected from among hydroxyl, primary, secondaryand tertiary amino, thiol, keto, thioketone, imine, carboxylic ester,carboxamide, amidine, urethane, urea, sulfoxide, sulfoximine,sulfonamide and sulfonic ester groups.

These functional groups are preferably self-complementary functionalgroups, i.e. the formation of the noncovalent bonds occurs between twoidentical functional groups of the ligands used. Functional groupscapable of tautomerism can each be present in the dimers in the form ofidentical or different isomers (tautomers). For instance, in the case ofketo-enol tautomerism, both mono(pseudo)pnicogen ligands can be in theketo form, both can be in the enol form or one can be in the keto formand the other in the enol form. Of course, the ligand/ligand pairs canalso be formed by two different ligands.

The distance between the atoms of the pnicogen-comprising orpseudopnicogen-comprising groups of the dimerized ligands whichcoordinate to the transition metal is preferably not more than 5 Å. Itis preferably in a range from 2.5 to 4.5 Å, particularly preferably from3.5 to 4.2 Å.

Suitable methods of determining whether the ligands used are capable offorming dimers include crystal structure analysis, nuclear magneticresonance spectroscopy and molecular modeling. The ligands inuncomplexed form can generally be employed for the determination. Thisapplies in particular to molecular modeling methods. In addition, it hasbeen found that crystal structure analysis carried out on the solid,nuclear magnetic resonance spectroscopy in solution and calculation ofthe structure for the gas phase all generally provide reliablepredictions regarding the behavior of the ligands used under thereaction conditions of the reaction being catalyzed. Thus, for example,ligands which according to the abovementioned methods of determinationare capable of forming dimers generally also display properties as areotherwise usual only for chelating ligands under the conditions of thereactions in which they are used. Such properties include, inparticular, achievement of a high stereoselectivity in the hydrogenationand hydroformylation of prochiral olefins. Furthermore, it has beenfound that this high stereoselectivity is no longer achieved when theformation of intermolecular noncovalent bonds between the ligands isdisrupted in the reaction by addition of acids or protic solvents suchas methanol.

In a suitable method of determining whether a ligand is suitable for theprocess of the invention, all possible hydrogen-bonded dimers of theligand and its tautomers are firstly produced by means of a graphicalmolecular modeling program. These dimer structures are then optimized bymeans of quantum-chemical methods. This is preferably done using densityfunctional theory (DFT), for example using Functional B-P86 (A. D.Becke, Phys. Rev. A 1988, 38, 3098; J. P. Perdew, Phys. Rev. B 1986, 33,8822; ibid 1986, 34, 7406(E)) and Basis SV(P) (A. Schäfer, H. Horn, R.Ahlrichs, J. Chem. Phys. 1992, 97, 2571) in the program packageTurbomole (R. Ahlrichs, M. Bär, M. Häser, H. Horn, C. Kölmel, Chem.Phys. Lett. 1989, 162, 165; M. v. Amim, R. Ahlrichs; J. Comput. Chem.1998, 19, 1746) (obtainable from the University of Karlsruhe). Asuitable commercially available molecular modeling package is Gaussian98 (M. J. Frisch, J. A. Pople et al., Gaussian 98, Revision A.5,Gaussian Inc., Pittsburgh (Pa.) 1998).

Preferred pseudochelating ligands are ones in which the distance betweenthe coordinating atoms, e.g. the P atoms, in the calculated dimerstructure is less than 5 Å.

For the purposes of the description of the present invention, theexpression “alkyl” comprises straight-chain and branched alkyl groups.These are preferably straight-chain or branched C₁-C₂₀-alkyl groups,more preferably C₁-C₁₂alkyl groups, particularly preferably C₁-C₈-alkylgroups and very particularly preferably C₁-C₄-alkyl groups. Examples ofalkyl groups are, in particular, methyl, ethyl, propyl, isopropyl,n-butyl, 2-butyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl,2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl,2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl,3-methylpentyl, 4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl,2,3-dimethylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl,3,3-dimethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl,1-ethylbutyl, 2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl,3-heptyl, 2-ethylpentyl, 1-propylbutyl, n-octyl, 2-ethylhexyl,2-propylheptyl, nonyl, decyl.

The expression “alkyl” also comprises substituted alkyl groups whichgenerally have 1, 2, 3, 4 or 5 substituents, preferably 1, 2 or 3substituents and particularly preferably 1 substituent. These arepreferably selected from among alkoxy, cycloalkyl, aryl, hetaryl,hydroxyl, halogen, NE¹E², NE¹E²E³⁺, carboxylate and sulfonate. Apreferred perfluoroalkyl group is trifluoromethyl.

For the purposes of the present invention, the expression “alkylene”refers to straight-chain or branched alkanediyl groups having from 1 to5 carbon atoms.

For the purposes of the present invention, the expression “cycloalkyl”comprises unsubstituted and substituted cycloalkyl groups, preferablyC₅-C₇-cycloalkyl groups such as cyclopentyl, cyclohexyl or cycloheptyl.If they are substituted, these can generally bear 1, 2, 3, 4 or 5substituents, preferably 1, 2 or 3 substituents and particularlypreferably 1 substituent. These substituents are preferably selectedfrom among alkyl, alkoxy, NE¹E², NE¹E²E³⁺ and halogen.

For the purposes of the present invention, the expression“heterocycloalkyl” comprises saturated, cycloaliphatic groups whichgenerally have from 4 to 7, preferably 5 or 6, ring atoms and in which 1or 2 of the ring carbons are replaced by heteroatoms selected from amongthe elements oxygen, nitrogen and sulfur and which may be substituted.If they are substituted, these heterocycloaliphatic groups can bear 1, 2or 3 substituents, preferably 1 or 2 substituents, particularlypreferably 1 substituent. These substituents are preferably selectedfrom among alkyl, alkoxy, aryl, COOR^(o), COO⁻M⁺, hydroxyl, halogen andNE¹E², with particular preference being given to alkyl radicals.Examples of such heterocycloaliphatic groups are pyrrolidinyl,piperidinyl, 2,2,6,6-tetramethylpiperidinyl, imidazolidinyl,pyrazolidinyl, oxazolidinyl, morpholidinyl, thiazolidinyl,isothiazolidinyl, isoxazolidinyl, piperazinyl, tetrahydrothienyl,tetrahydrofuranyl, tetrahydropyranyl, dioxanyl.

For the purposes of the present invention, the expression “aryl”comprises unsubstituted and substituted aryl groups and preferablyrefers to phenyl, tolyl, xylyl, mesityl, naphthyl, fluorenyl,anthracenyl, phenanthrenyl or naphthacenyl, particularly preferablyphenyl or naphthyl. If they are substituted, these aryl groups cangenerally bear 1, 2, 3, 4 or 5 substituents, preferably 1, 2 or 3substituents and particularly preferably 1 sustituent, selected fromamong the groups alkyl, alkoxy, carboxylate, trifluoromethyl, sulfonate,NE¹E², alkylene-NE¹E², nitro, cyano and halogen. A preferredperfluoroaryl group is pentafluorophenyl.

For the purposes of the present invention, the expression “hetaryl”comprises unsubstituted or substituted, heterocycloaromatic groups,preferably the groups furyl, thienyl, pyridyl, quinolinyl, acridinyl,pyridazinyl, pyrimidinyl, pyrazinyl, pyrrolyl, imidazolyl, pyrazolyl,indolyl, purinyl, indazolyl, benzotriazolyl, 1,2,3-triazolyl,1,3,4-triazolyl and carbazolyl. If they are substituted, theseheterocycloaromatic groups can generally bear 1, 2 or 3 substituentsselected from among the groups alkyl, alkoxy, hydroxyl, carboxylate,sulfonate NE¹E², alkylen-NE¹E² and halogen.

For the purposes of the present invention, carboxylate and sulfonate arepreferably derivatives of a carboxylic acid function or a sulfonic acidfunction, in particular a metal carboxylate or sulfonate, a carboxylicester or sulfonic ester function or a carboxamide or sulfonamidefunction. Such derivatives include, for example, the esters withC₁-C₄-alkanols such as methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol and tert-butanol.

What has been said above with regard to the expressions “alkyl”,“cycloalkyl”, “aryl”, “heterocycloalkyl” and “hetaryl” appliesanalogously to the expressions “alkoxy”, “cycloalkoxy”, “aryloxy”,“heterocycloalkoxy” and “hetaryloxy”.

For the purposes of the present invention, the expression “acyl” refersto alkanoyl or aroyl groups generally having from 2 to 11, preferablyfrom 2 to 8, carbon atoms, for example the formyl, acetyl, propanoyl,butanoyl, pentanoyl, hexanoyl, heptanoyl-, 2-ethylhexanoyl,2-propylheptanoyl, benzoyl or naphthoyl group.

The radicals E¹ to E¹² are selected independently from among hydrogen,alkyl, cycloalkyl and aryl. The groups N¹E², NE⁴E⁵, NE⁷E⁸ and NE¹⁰E¹¹are preferably N,N-dimethylamino, N,N-diethylamino, N,N-dipropylamino,N,N-diisopropylamino, N,N-di-n-butylamino, N, N-di-t-butylamino, N,N-dicyclohexylamino or N, N-diphenylamino.

Halogen is fluorine, chlorine, bromine or iodine, preferably fluorine,chlorine or bromine.

M⁺ is a cation equivalent, i.e. a monovalent cation or the part of apolyvalent cation corresponding to a single positive charge. The cationM⁺ serves merely as counterion to neutralize negatively chargedsubstituent groups such as the COO⁻ or sulfonate group and can inprinciple be selected freely. Preference is therefore given to usingalkali metal ions, in particular Na⁺, K⁺, Li⁺ ions, or onium ions, suchas ammonium, monoalkylammonium, dialkylammonium, trialkylammonium,tetraalkylammonium, phosphonium, tetraalkylphosphonium ortetraarylphosphonium ions.

An analogous situation applies to the anion equivalent X⁻ which servesmerely as counterion of positively charged substituent groups such asammonium groups and can be selected freely from among monovalent anionsand the parts of a polyvalent anion corresponding to a single negativecharge. Preference is generally given to halide ions X⁻, in particularchloride and bromide.

x and y are each an integer from 1 to 240, preferably an integer from 2to 120.

For the purposes of the present invention, the term “polycycliccompound” comprises in the broadest sense compounds which comprise atleast two rings, regardless of the way in which these rings are linked.The rings can be carbocyclic and/or heterocyclic. The rings can belinked via single or double bonds (“multinuclear compounds”), be joinedby fusion (“fused ring systems”) or be bridged (“bridged ring systems”,“cage compounds”). Preferred pplycyclic compounds are fused ringsystems.

Fused ring systems can be aromatic, hydroaromatic and cyclic compoundsjoined by fusion. Fused ring systems comprise two, three or more rings.Depending on the way in which the rings are linked, a distinction ismade in the case of fused ring systems between ortho-fusion, i.,e. eachring shares an edge or two atoms with each adjacent ring, andperi-fusion in which one carbon atom belongs to more than two rings.Among fused ring systems, preference is given to ortho-fused ringsystems.

The ligand/ligand pairs used according to the invention can berepresented schematically by the formula I:

where

-   the atoms Pn are independently selected pnicogen atoms or    coordinating atoms of pseudopnicogen-comprising groups,-   A and B are radicals of mutually complementary functional groups    between which there is a noncovalent interaction,-   R¹ is a singly or doubly bonded organyl radical,-   R² is a singly bonded organyl radical,-   a is, depending on the valence of the pnicogen atom or coordinating    atom of the pseudopnicogen-comprising groups and the number of    coordination sites occupied by the radical R², 0 or 1,    where the pnicogen atom or coordinating atom of the    pseudopnicogen-comprising group can, together with at least two of    the radicals R¹, R² and A or B bound thereto, also be part of a ring    system.

The Pn atoms in the formula I are preferably selected independently fromamong N, P, As, Sb and carbene carbon atoms.

In a first variant, the pnicogen- or pseudopnicogen-comprising group isa carbene group of the formula R¹—C-A or R¹—C—B. The carbene carbon atomis then preferably part of a ring system of the formula I.1

where

-   G¹ is NR⁸ or CR^(C)R^(D), where R^(B), R^(C) and R^(D) are each,    independently of one another, hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl, where R^(C) or R^(D) may also be    one bond equivalent of a double bond,-   Q¹ is a divalent bridging group having from 1 to 5 atoms between the    flanking bonds,-   R^(A) is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or    hetaryl,    where one of the radicals R^(A), R^(B), R^(C), R^(D) or a radical on    the group Q¹ is a functional group capable of forming    intermolecular, noncovalent bonds or comprises such a group.

The compounds of the formula I.1 are preferably selected from among theN-heterocyclic carbenes of the formula I.1a to I.1d

where

-   R^(A), R^(B), R^(C), R^(E) and R^(F) are each, independently of one    another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or    hetaryl, where one of these radicals is a functional group capable    of forming intermolecular, noncovalent bonds or comprises such a    group.

In the compounds of the formulae I.1a to I.1d, the radicals R^(A),R^(B), R^(C), R^(E) and R^(F) which are not a functional group capableof forming intermolecular, noncovalent bonds or comprise such a groupare preferably unsubstituted or monosubstituted or polysubstituted alkylor aryl radicals.

The radical R^(A) in the compounds of the formulae I.1a to I.1d ispreferably a functional group capable of forming intermolecular,noncovalent bonds or comprises such a group.

In a second variant, the pnicogen- or pseudopnicogen-comprising group isan imine group of the formula R¹═N-A or R¹═N—B. The imine group is thenpreferably part of a ring system of the formula I.2

where

-   Q² is a divalent bridging group having from 1 to 5 atoms between the    flanking bonds, and-   R^(G), R^(H) and R^(I) are each, independently of one another,    hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl,    where one of the radicals R^(G), R^(H), R^(I) or a radical on the    group Q² is a functional group capable of forming intermolecular,    noncovalent bonds or comprise such a group.

The group Q² in the formula I.2 is preferably a C₁-C₅-alkylene groupwhich can contain a heteroatom or a heteroatom-comprising group,preferably selected from among O, S or NR^(K) (R^(K)=hydrogen, alkyl,cycloalkyl, aryl).

The compounds of the formula I.2 are preferably selected from amongcyclic imines of the formulae I.2a and I.2b

where

-   G² is O or NR^(K), where R^(K) is hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl,-   R^(G), R^(H), R^(I) and R^(L) are each, independently of one    another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or    hetaryl,    where one of the radicals R^(G), R^(H), R^(I), R^(K) and R^(L) is a    functional group capable of forming intermolecular, noncovalent    bonds or comprises such a group.

The radical R^(G)in the compounds of the formulae I.2a and I.2b ispreferably a functional group capable of forming intermolecular,noncovalent bonds or comprises such a group.

The radical R^(H) in the compounds of the formulae I.2a and I.2b ispreferably alkyl, in particular methyl, ethyl, isopropyl or tert-butyl,aryl, in particular phenyl, or arylalkyl, in particular benzyl.

The radicals R^(I) and R^(L) in the compounds of the formulae I.2a andI.2b are preferably each hydrogen.

The group G² in the compounds of the formulae I.2a and I.2b ispreferably O or NR^(K).

In a third variant, the pnicogen- or pseudopnicogen-comprising group isselected from among groups of the formula I.3

where

-   Pn is N, P, As or Sb, preferably P,-   R¹ and R² are each, independently of one another, alkyl, alkoxy,    cycloalkyl, cycloalkoxy, heterocycloalkyl, heterocycloalkoxy, aryl,    aryloxy, hetaryl or hetaryloxy or-   R¹ and R² together with the phosphorus atom to which they are    bound-form a 4- to 8-membered heterocycle which may additionally be    fused with one, two or three cycloalkyl, heterocycloalkyl, aryl or    hetaryl groups, where the heterocycle and, if present, the fused-on    groups may each bear, independently of one another, one, two, three    or four substituents selected from among alkyl, cycloalkyl,    heterocycloalkyl, aryl, hetaryl, COOR^(c), COO⁻M⁺, SO₃R^(c), SO₃    ⁻M⁺, PO₃(R^(c))(R^(d)), (PO₃)²⁻(M⁺)₂, NE⁴E⁵, (NE⁴E⁵E⁶)⁺X⁻, OR^(e),    SR^(e), (CHR^(f)CH₂O)_(y)R^(e), (CH₂O)_(y)R^(e),    (CH₂CH₂NE⁴)_(y)R^(e), halogen, nitro, acyl and cyano,    -   where    -   R^(c) and R^(d) are identical or different radicals selected        from among hydrogen, alkyl, cycloalkyl, aryl and hetaryl,    -   R^(e), E⁴, E⁵, E⁶ are identical or different radicals selected        from among hydrogen, alkyl, cycloalkyl, aryl and hetaryl,    -   R^(f) is hydrogen, methyl or ethyl,    -   M⁺ is a cation equivalent,    -   X⁻ is an anion equivalent and    -   y is an integer from 1 to 240.

In a first preferred embodiment, the radicals R¹ and R² in the groups ofthe formula I.3 are not bridged. R¹ and R² are then preferably selected,independently of one another, from among alkyl, cycloalkyl, aryl andhetaryl, as defined at the outset.

Preferably at least one R¹ and R² is aryl and more preferably both R¹and R² are aryl. For example, one of the radicals R¹ and R² is thenphenyl and the other is naphthyl or R¹ and R² are both phenyl or R¹ andR² are both naphthyl. Preferred naphthyl radicals are 1-naphthylradicals.

In a further preferred embodiment, the radicals R¹ and R² in the groupsof the formula I.3 are bridged. The pnicogen-comprising group is thenpreferably a group of the formula

where

-   Pn is P, As or Sb, preferably P,-   r and s are each, independently of one another, 0 or 1, and-   D together with the phosphorus atom and the oxygen atom(s) to which    it is bound forms a 4- to 8-membered heterocycle which may be fused    with one, two or three cycloalkyl, heterocycloalkyl, aryl and/or    hetaryl groups, where the fused-on groups may each independently of    one another bear one, two, three or four substituents selected from    among alkyl, alkoxy, halogen, sulfonate, NE⁴E⁵, alkylene-NE⁴E⁵,    nitro, cyano and carboxylate, and/or D may bear one, two, three or    four substituents selected from among alkyl, hydroxy, alkoxy,    optionally substituted cycloalkyl and optionally substituted aryl,    and/or D may be interrupted by 1, 2 or 3 optionally substituted    heteroatoms.

The radical D is preferably a C₂-C₆-alkylene bridge which has 1 or 2aryl groups fused onto it and/or may bear a substituent selected fromamong alkyl, optionally substituted cycloalkyl and optionallysubstituted aryl and/or may be interrupted by an optionally substitutedheteroatom.

The fused-on aryls of the radicals D are preferably benzene ornaphthalene. Fused-on benzene rings are preferably unsubstituted or have1, 2 or 3, in particular 1 or 2, substituents which are preferablyselected from among alkyl, alkoxy, halogen, sulfonate, NE⁴E⁵,alkylene-NE⁴E⁵, trifluoromethyl, nitro, carboxylate, alkoxycarbonyl,acyl and cyano. Fused-on naphthalenes are preferably unsubstituted orhave 1, 2 or 3, in particular 1 or 2, of the substituents mentionedabove in the case of the fused-on benzene rings in the ring which is notfused on and/or in the fused-on ring. In the case of the substituents onthe fused-on aryls, alkyl is preferably C₁-C₄-alkyl and in particularmethyl, isopropyl or tert-butyl. Alkoxy is preferably C₁-C₄-alkoxy andin particular methoxy. Alkoxycarbonyl is preferablyC₁-C₄-alkoxycarbonyl.

If the C₂-C₆-alkylene bridge of the radical D is interrupted by 1, 2 or3 optionally substituted heteroatoms, these are preferably selected fromamong O, S and NR^(h), where R^(h) is alkyl, cycloalkyl or aryl.

If the C₂-C₆-alkylene bridge of the radical D is substituted itpreferably bears 1, 2, 3 or 4, in particular 2 or 4, substituentsselected from among alkyl, alkoxy, hydroxy, cycloalkyl,heterocycloalkyl, aryl and hetaryl, where the cycloalkyl,heterocycloalkyl, aryl and hetaryl substituents may each bear 1, 2 or 3of the substituents mentioned at the outset as being suitable for theseradicals.

The radical D is preferably a C₃-C₆-alkylene bridge which, as indicatedabove, is fused and/or substituted and/or interrupted by optionallysubstituted heteroatoms. In particular, the radical D is aC₃-C₆-alkylene bridge which is fused with one or two phenyl and/ornaphthyl groups, where the phenyl or naphthyl groups may bear 1, 2 or 3of the abovementioned substituents.

Preference is given to the radical D together with the phosphorus atomand the oxygen atom(s) to which it is bound forming a 4- to 8-memberedheterocycle. In this case D is a radical selected from among theradicals of the formulae II.1 to II.4,

where

-   T is O, S or NR^(I), where    -   R^(I) is alkyl, cycloalkyl or aryl,-   or T is a C₁-C₃-alkylene bridge which may have a double bond and/or    an alkyl, cycloalkyl or aryl substituent, where the aryl substituent    may bear one, two or three of the substituents mentioned for aryl,-   or T is a C₂-C₃-alkylene bridge which is interrupted by O, S or    NR^(I),-   R^(I), R^(II), R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII),    R^(IX), R^(X), R^(XI) and R^(XII) are each, independently of one    another, hydrogen, alkyl, cycloalkyl, aryl, alkoxy, halogen,    sulfonate, NE⁴E⁵, alkylene-NE⁴E⁵, trifluoromethyl, nitro,    alkoxycarbonyl or cyano.

In a particularly preferred embodiment, the radicals R¹ and R² in thegroups of the formula I.3 are bridged in such a way that thephosphorus-comprising group of the formula

is a chiral heterocycle. The bridging groups D are then preferablyselected from among groups of the formulae II.1 and II.3, where

-   R^(I), R^(II), R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII),    R^(IX), R^(X), R^(XI) and R^(XII) are each, independently of one    another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl,    hetaryl, hydroxy, thiol, polyalkylene oxide, polyalkylenimine,    alkoxy, halogen, SO₃H, suifonate, NE⁴E⁵, alkylene-NE⁴E⁵,    trifluoromethyl, nitro, alkoxycarbonyl, carboxyl, acyl and cyano,    where E⁴ and E⁵ are identical or different radicals selected from    among-hydrogen, alkyl, cycloalkyl and aryl.

Preference is also given to Y being a group of the formula II.1 in whichR^(IV) and R^(V) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. R^(IV) and R^(V) are preferably selected from amongmethyl, ethyl, isopropyl, tert-butyl and methoxy. In these compounds,R^(I), R^(II), R^(III), R^(VI), R^(VII) and R^(VIII) are preferably eachhydrogen.

Preference is also given to Y being a group of the formula II.1 in whichR^(I) and R^(VIII) are each, independently of one another, C₁-C₄-alkylor C₁-C₄-alkoxy. R^(I) and R^(VIII) are particularly preferablytert-butyl. In these compounds, R^(II), R^(III), R^(IV), R^(V), R^(VI),R^(VII) are particularly preferably each hydrogen. Preference is alsogiven to R^(III) and R^(VI) in these compounds being, independently ofone another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(III) and R^(VI) areparticularly preferably selected independently from among methyl, ethyl,isopropyl, tert-butyl and methoxy.

Preference is also given to Y being a group of the formula II.1 in whichR^(II) and R^(VII) are each hydrogen. In these compounds, preference isgiven to R^(I), R^(III), R^(IV), R^(V), R^(VI) and R^(VIII) each being,independently of one another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(I),R^(III), R^(IV), R^(V), R^(VI) and R^(VIII) are particularly preferablyselected independently from among methyl, ethyl, isopropyl, tert-butyland methoxy.

Preference is also given to Y being a group of the formula II.3 in whichR^(I) to R^(XII) are each hydrogen.

Preference is also given to Y being a group of the formula II.3 in whichR^(I) and R^(XII) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. In particular, R^(I) and R^(XII) are selectedindependently from among methyl, ethyl, isopropyl, tert-butyl, methoxyand alkoxycarbonyl, preferably methoxycarbonyl. In these compounds, theradicals R^(II) to R^(XI) are particularly preferably each hydrogen.

Preferred chiral groups of the general formula I.3 include, for example,(2R, 3S, 4R, 5S)-2,5-dimethyl-3,4-dihydroxyphospholano and (2S, 3R, 4S,5R)-2,5-dimethyl-3,4-dihydroxyphospholano groups and also(R)-1,1′-binaphthylene-2,2′-diyldioxyphosphino,(S)-1,1′-binaphthylene-2,2′-diyldioxyphosphino,(S)-1,1′-biphenylene-2,2′-diyldioxyphosphino and(S)-1,1′-biphenylene-2,2′-diyldioxyphosphino groups which may beunsubstituted or, as described above, substituted.

Preference is given to at least one of the ligands used according to theinvention having a functional group capable of tautomerism and capableof forming intermolecular noncovalent bonds. This group is preferablyselected from among groups of the formula

and the tautomers thereof, where Y is O, S or NR⁴ and R⁴ is hydrogen,alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl.

The position of the respective equilibrium between the tautomers isdependent, inter alia, on the group Y and on the substituents on thegroup capable of tautomerism. The equilibrium is shown below for theexamples of keto-enol tautomerism and imineenamine tautomerism:

The ligands used according to the invention preferably comprise at leastone structural element of the formula I.a or I.b

or tautomers thereof, where

-   Pn, R¹, R² and a are as defined above,-   R³ is hydrogen, alkyl, alkoxy, cycloalkyl, cycloalkoxy,    heterocycloalkyl, heterocycloalkoxy, aryl, aryloxy, hetaryl or    hetaryloxy,-   X is a divalent bridging group having from 1 to 5 bridge atoms    between the flanking bonds,-   Y is O, S or NR⁴, where R⁴ is hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl,    where two or more of the radicals X and R¹ to R⁴ together with the    structural element of the formula I.a or I.b to which they are bound    may form a monocyclic or polycyclic compound.

With regard to suitable and preferred radicals R¹ and R², reference ismade to what has been said above.

In the compounds of the formulae I.a and I.b, Pn is preferably N, P, Asor Sb, particularly preferably P, As or Sb and in particular P.

The divalent bridging group X in the compounds of the formulae I.a andI.b preferably has from 1 to 4, particularly preferably from 1 to 3,bridge atoms between the flanking bonds.

The divalent bridging group X is preferably a C₁-C₅-alkylene bridgewhich, depending on the number of bridge atoms, may have one or twodouble bonds and/or one, two, three or four substituents selected fromamong alkyl, cycloalkyl, heterocycloalkyl, aryl, hetaryl, carboxylate,sulfonate, phosphonate, NE¹E² (E¹, E²=hydrogen, alkyl, cycloalkyl, acylor aryl), hydroxy, thiol, halogen, nitro, acyl and cyano, where thecycloalkyl, aryl and hetaryl substituents may additionally bear one, twoor three substituents selected from among alkyl, alkoxy, halogen,trifluoromethyl, nitro, alkoxycarbonyl and cyano, and/or one or twononadjacent bridge atoms of the C₁-C₅-alkylene bridge X may be replacedby a heteroatom or a heteroatom-comprising group and/or the alkylenebridge X can have one or two aryl and/or hetaryl groups fused onto it,where the fused-on aryl and hetaryl groups may each bear one, two orthree substituents selected from among alkyl, cycloalkyl, aryl, alkoxy,cycloalkoxy, aryloxy, acyl, halogen, trifluoromethyl, nitro, cyano,carboxyl, alkoxycarbonyl and NE¹E² (E¹ and E²=hydrogen, alkyl,cycloalkyl, acyl or aryl) and/or two or more bridge atoms of theC₁-C₅-alkylene bridge X together with the structural element of theformula I.a or I.b to which they are bound may form a monocyclic orpolycyclic compound.

X is preferably a C₁-C₅-alkylene bridge which can have one or two doublebonds. Preference is also given to two or more of the bridge atoms ofthe bridge X together with the structural element of the formula I.a orI.b to which they are bound forming a monocyclic or polycyclic compound.

The ligands used according to the invention preferably have at least onestructural element of the formula I.a or I.b in which the group X andthe radical R³ together with the group —NH—C(═Y)— to which they arebound form a 5- to 8-membered, preferably 6-membered ring. This ring canhave one, two or three double bonds, where one of these double bonds canbe due to the tautomeric group —N═C(YH)—. Preference is given to6-membered rings which, allowing for the tautomerism, have three doublebonds. Such ring systems in which one of the tautomers can form anaromatic ring system are particularly stable. The rings mentioned can beunsubstituted or can bear one, two, three, four or five of theabovementioned substituents. These are preferably selected from amongC₁-C₄-alkyl, particularly preferably methyl, ethyl, isopropyl ortert-butyl, C₁-C₄-alkoxy, especially methoxy, ethoxy, isopropyloxy ortert-butyloxy, and aryl, preferably phenyl. In one useful embodiment,the rings mentioned have at least one double bond and the radicals boundto this double bond form a fused ring system having 1, 2 or 3 furtherrings. These are preferably benzene rings or naphthalene units. Fused-onbenzene rings are preferably unsubstituted or have 1, 2 or 3substituents selected from among alkyl, hydroxy, alkoxy, carboxylate,sulfonate, halogen, NE¹E², trifluoromethyl, nitro, alkoxycarbonyl, acyland cyano. Fused-on naphthalene units are preferably unsubstituted orhave 1, 2 or 3 of the substituents mentioned above in the case of thefused-on benzene rings in the ring which is not fused on and/or in thefused-on ring.

The ligands used according to the invention are preferably selected fromamong compounds of the formulae I.A to I.C

and the tautomers thereof, where

-   one of the radcals R⁵ to R⁹ is a pnicogen- or    pseudopnicogen-comprising group as defined above,    the radicals R⁵ to R⁹ which are not a pnicogen- or    pseudopnicogen-comprising group are each, independently of one    another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl,    hetaryl, WCOOR^(o), WCOO⁻M⁺, W(SO₃)R^(o), W(SO₃)⁻M⁺,    WPO₃(R^(o))(R^(p)), W(PO₃)²⁻M⁺)₂, WNE¹E², W(NE¹E²E³)⁺X⁻, WOR^(q),    WSR^(q), (CHR^(r)CH₂O)_(x)R^(q), (CH₂NE¹)_(x)R^(q),    (CH₂CH₂NE¹)_(x)R^(q), halogen, nitro, acyl or cyano,    where-   W is a single bond, a heteroatom, a heteroatom-comprising group or a    divalent bridging group having from 1 to 20 bridge atoms,-   R^(o) and R^(p) are identical or different radicals selected from    among alkyl, cycloalkyl, acyl and aryl,-   R^(q), E¹, E², E³ are identical or different radicals selected from    among hydrogen, alkyl, cycloalkyl, acyl and aryl,-   R^(r) is hydrogen, methyl or ethyl,-   M⁺ is a cation equivalent,-   X⁻ is an anion equivalent and-   x is an integer from 1 to 240,-   where two vicinal radicals R⁵ to R⁹ may also form a fused ring    system, and-   R^(a)and R^(b) are each hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl, and R^(a) can also be acyl.

Suitable pnicogen- or pseudopnicogen-comprising groups of the compounds(I.A) to (I.C) are the groups I.1, I.2 and I.3 mentioned above. Suitableand preferred embodiments of these groups are incorporated by reference.

The pnicogen- or pseudopnicogen-comprising groups of the compounds (I.A)to (I.C) are preferably selected from among groups of the formula—W′—PnR¹R², where

-   Pn is N, P, As or Sb, in particular P, As or Sb, especially P,-   W′ is a single bond, a heteroatom, a heteroatom-comprising group or    a divalent bridging group having from 1 to 4 bridge atoms between    the flanking bonds,-   R¹ and R² are as defined above.

If two vicinal radicals selected from among the radicals R⁵ to R⁹ in thecompounds of the formulae I.A to I.C which are not a pnicogen- orpseudopnicogen-comprising group form a fused ring system, these arepreferably the radicals R⁷ and R⁸. The fused-on rings are preferablybenzene rings or naphthalene units.

Fused-on benzene rings are preferably unsubstituted or have 1, 2 or 3substituents which are preferably selected from among alkyl, hydroxy,alkoxy, carboxylate, sulfonate, halogen, NE¹E², trifluoromethyl, nitro,alkoxycarbonyl, acyl and cyano. Fused-on naphthalene units arepreferably unsubstituted or have 1, 2 or 3 of the substituents mentionedabove in the case of the fused-on benzene rings in the ring which is notfused on and/or in the fused-on ring.

When the radical R^(a) in the compounds of the formula I.B is acyl, thisacyl radical is preferably selected from among radicals of the formula—C(═O)—R^(k), where R^(k) is hydrogen, alkyl, cycloalkyl, aryl orhetaryl. R^(k) is preferably C₁-C₄-alkyl, in particular methyl, ethyl,n-propyl, isopropyl, n-butyl or tert-butyl. A preferred acyl radicalR^(a) is the pivaloyl radical.

The compounds of the formulae I.A to I.C are suitable as ligands incatalysts for asymmetric syntheses regardless of their ability to formintermolecular, noncovalent bonds. The invention therefore also providesa process for preparing chiral compounds by reacting a prochiralcompound comprising at least one ethylenically unsaturated double bondwith a substrate in the presence of a chiral catalyst comprising atleast one transition metal complex with ligands selected from amongcompounds of the formulae I.A to I.C as defined above.

The ligands used according to the invention are preferably selected fromamong compounds of the formulae I.i to I.iii

and the tautomers thereof, where

-   b is 0 or 1,-   Pn is a pnicogen- or pseudopnicogen-comprising group, preferably N,    P, As or Sb, in particular P, As or Sb, especially P,-   R¹ and R² are as defined above,-   R⁶ to R⁹ are each, independently of one another, hydrogen,    C₁-C₄-alkyl, C₁-C₄-alkoxy, aryl, heteroaryl, acyl, halogen,    C₁-C₄-alkoxycarbonyl or carbo)ylate,-   where two vicinal radicals R⁶ to R⁹ may also form a fused ring    system, and-   R^(a) and R^(b) are each hydrogen, alkyl, cycloalkyl or aryl, and    R^(a) can also be acyl.

In the compounds of the formulae I.i to I.iii, the radicals R¹ and R²are preferably each, independently of one another, C₁-C₈-alkyl such asmethyl, ethyl, isopropyl and tert-butyl, C₅-C₈-cycloalkyl such ascyclohexyl or aryl such as phenyl. Preference is given to both theradicals R¹ and R² being aryl. In particular, one of the radicals R¹ andR² is phenyl and the other is naphthyl or R¹ and R² are both phenyl orR¹ and R² are both naphthyl. Preferred naphthyl radicals are 1-naphthylradicals.

Preference is also given to compounds of the formulae I.i to I.iii inwhich the radicals R¹ and R² are bridged so that they form apnicogen-comprising group of the formula

where Pn, D, r and s are as defined above.

In a particular embodiment, the pnicogen-comprising group is a chiralpnicogen-comprising group as described above. Reference is made to whathas been said with regard to the groups II.1 and II.3.

The radicals R⁶, R⁷, R⁸ and R⁹ in the compounds I.i to I.iii arepreferably selected independently from among hydrogen, C₁-C₄-alkyl,C₁-C₄-alkoxy, aryl, heteroaryl, carboxylate, sulfonate, NE¹E², halogen,trifluoromethyl, nitro, alkoxycarbonyl, acyl and cyano. R⁶, R⁷, R⁸ andR⁹ are preferably hydrogen, aryl or heteroaryl.

Preference is also given to the radicals R⁷ and R⁸ in the compounds I.ito I.iii forming a fused-on ring system.

In the compound of the formula I.ii, the radical R^(a) is preferablyhydrogen, C₁-C₈-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₀-aryl. Preference isalso given to the radical R^(a) in the formula I.ii being acyl asdefined above. In particular, R^(a) is —C(═O)—R^(k) whereR^(k)═C₁-C₄-alkyl, in particular tert-butyl.

In the compounds of the formula I.iii the radical R^(b) is preferablyhydrogen, C₁-C₈-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₀-aryl or hetaryl.

A preferred ligand of the formula I.i is

and the tautomers thereof.

Preferred ligands of the formula I.ii are

and the tautomers thereof.

The ligand/ligand pairs according to the invention and those usedaccording to the invention can be pairs of identical or differentligands.

Examples of ligands which can be used according to the invention are thefollowing structures:

Examples of ligands which are preferred according to the invention are

-   6-[(R)-1,1′-binaphthylene-2,2′-diyldioxyphosphino]-1-H-pyridin-2-one,-   6-[(S)-1,1′-binaphthylene-2,2′-diyldioxyphosphino]-1-H-pyridin-2-one,    and-   6-(3,5-dioxa-4-phosphacyclohepta[2,1-a,3,4-a]dinaphthalen-4-yloxy)-1H-pyridin-2-one.

The preparation of ligands which can be used according to the inventioncan be carried out by conventional methods known to those skilled in theart.

The invention further provides a chiral catalyst as described above.What has been said above with regard to suitable and preferred ligandsis fully incorporated by reference at this point.

The chiral catalysts of the invention and those used according to theinvention preferably comprise two or more of the above-describedcompounds as ligands. At least two of the ligands are preferably presentin dimerized form (as ligand/ligand pairs). The ligand/ligand pairs canbe made up of identical or different ligands. In addition to the ligandsdescribed above, they can further comprise at least one additionalligand which is preferably selected from among halides, amines,carboxylates, acetylacetonate, arylsulfonates and alkylsulfonates,hydride, CO, olefins, dienes, cycloolefins, nitrites, N-comprisingheterocycles, aromatics and heteroaromatics, ethers, PF₃, phospholes,phosphabenzenes and monodentate, bidentate and polydentate phosphine,phosphinite, phosphonite, phosphoramidite and phosphite ligands.

The transition metal is preferably a metal of transition group I, VI,VII or VIII of the Periodic Table of the Elements. The transition metalis more preferably selected from among the metals of transition groupVIII (i.e. Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt). In particular, thetransition metal is iridium, nickel, ruthenium, rhodium, palladium orplatinum.

The present invention provides a quite general process for preparingchiral compounds by reacting a prochiral compound comprising at leastone ethylenically unsaturated double bond with a substrate in thepresence of a chiral catalyst as described above. It is merely necessaryfor at least one of the ligands used or the overall catalytically activespecies to be chiral. In general, particular transition metal complexesare formed as catalytically active species under the reaction conditionsof the individual processes for preparing chiral compounds. Thus, forexample, the catalysts or catalyst precursors used in each case areconverted under hydroformylation conditions into catalytically activespecies of the formula H_(x)M_(y)(CO)_(z)L_(q), where M is a transitionmetal, L is a pnicogen-comprising compound and q, x, y, z are integerswhich depend on the valence and type of the metal and on the number ofcoordination sites occupied by the ligand L. It is preferred that z andq each have, independently of one another, a value of at least 1, e.g.1, 2 or 3. The sum of z and q is preferably from 1 to 5. If desired, thecomplexes may further comprise at least one of the above-describedadditional ligands. There is reason to assume that the respectivecatalytically active species also comprises dimerized ligands(pseudochelates).

The catalytically active species is preferably present as a homogeneoussingle-phase solution in a suitable solvent. This solution can furthercomprise free ligand.

The process of the invention for preparing chiral compounds ispreferably a hydrogenation, hydroformylation, hydrocyanation,carbonylation, hydroacylation (intramolecular and intermolecular),hydroamidation, hydroesterification, hydrosilylation, hydroboration,aminolysis (hydroamination), alcoholysis (hydroxy-alkoxy addition),isomerization, transfer hydrogenation, metathesis, cyclopropanation,aldol condensation, allylic alkylation or a [4+2]-cycloaddition(Diels-Alder reaction).

The process of the invention for preparing chiral compounds is morepreferably a 1,2-addition, in particular a hydrogenation or a1-hydro-2-carboaddition. For the purposes of the present invention, a1,2-addition is an addition onto the two adjacent atoms of a C═X doublebond (X═C, heteroatom). A 1-hydro-2-carboaddition is an additionreaction in which hydrogen is bound to one atom of the double bond and acarbon-comprising group is bound to the other after the reaction. Doublebond isomerizations during the addition reaction are permitted. For thepurposes of the present invention, the use of the term1-hydro-2-carboaddition in the case of unsymmetrical substrates does notimply preferential addition of the carbon fragment onto the C2 atom,since the selectivity in respect of the orientation of the addition isgenerally dependent on the agent to be added on and the catalyst used.The term “1-hydro-2-carboaddition” is thus equivalent to“1-carbo-2-hydroaddition”.

The reaction conditions of the process of the invention for preparingchiral compounds generally correspond, except for the chiral catalystused, to those of the corresponding asymmetric processes. A personskilled in the art can thus find suitable reactors and reactionconditions for the respective process in the relevant literature andadapt them in a routine fashion. Suitable reaction temperatures aregenerally in a range from −100 to 500° C., preferably in a range from−80 to 250° C. Suitable reaction pressures are generally in a range from0.0001 to 600 bar, preferably from 0.5 to 300 bar. The processes cangenerally be carried out continuously, semicontinuously or batchwise.Suitable reactors for a continuous reaction are known to those skilledin the art and are described, for example, in Ullmanns Enzyklopädie dertechnischen Chemie, Vol. 1, 3^(rd) edition, 1951, p. 743 ff. Suitablepressure-rated reactors are likewise known to those skilled in the artand are described, for example, in Ullmanns Enzyklopädie der technischenChemie, Vol. 1, 3^(rd) edition, 1951, p. 769 ff.

The processes of the invention can be carried out in a suitable solventwhich is inert under the respective reaction conditions. Generallysuitable solvents are, for example, aromatics such as toluene andxylenes, hydrocarbons or mixtures of hydrocarbons. Further suitablesolvents are halogenated, in particular chlorinated, hydrocarbons suchas dichloromethane, chloroform or 1,2-dichloroethane. Further possiblesolvents are esters of aliphatic carboxylic acids with alkanols, forexample ethyl acetate or Texanol®, ethers such as tert-butyl methylether, 1,4-dioxane and tetrahydrofuran and also dimethytformamide. Inthe case of sufficiently hydrophilic ligands, it is also possible to usealcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol,isobutanol, ketones such as acetone and methyl ethyl ketone, etc.Furthermore, “ionic liquids” can also be used as solvents. These areliquid salts, for example N,N′-dialkylimidazolium salts such asN-butyl-N′-methylimidazolium salts, tetraalkyl-ammonium salts such astetra-n-butylammonium saltse, N-alkylpyridinium salts such asn-butylpyridinium salts, tetraalkylphosphonium salts such astrishexyl(tetradecyl)phosphonium salts, e.g. the tetrafluoroborates,acetates, tetrachloroaluminates, hexafluorophosphates, chlorides andtosylates. It is also possible to use a starting material, product orby-product of the respective reaction as solvent.

As prochiral ethylenically unsaturated compounds for the process of theinvention, it is in principle possible to use all prochiral compoundswhich comprise one or more ethylenically unsaturated carbon-carbon orcarbon-heteroatom double bonds. These include prochiral olefins ingeneral (hydroformylation, intermolecular hydroacylation,hydrocyanation, hydrosilylation, carbonylation, hydroamidation,hydroesterification, aminolysis, alcoholysis, cyclopropanation,hydroboration, Diels-Alder reaction, metathesis), unsubstituted andsubstituted aldehydes (intramolecular hydroacylation, aldolcondensation, allylic alkylation), ketones (hydrogenation,hydrosilylation, aldol condensation, transfer hydrogenation, allylicalkylation) and imines (hydrogenation, hydrosilylation, transferhydrogenation, Mannich reaction).

Suitable prochiral ethylenically unsaturated olefins are generallycompounds of the formula

where R^(α) and R^(β) and/or R^(γ) and R^(δ) are radicals of differentdefinitions. It is self-evident that to prepare chiral compoundsaccording to the invention, the substrates reacted with the prochiralethylenically unsaturated compound and sometimes also thestereo-selectivity in respect of the addition of a particularsubstituent onto a particular carbon atom of the C—C double bond arechosen so that at least one chiral carbon atom results.

Subject to the abovementioned condition, R^(α), R^(β), R^(γ) and R^(δ)are preferably selected independently from among hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy,heterocycloalkoxy, aryloxy, hetarylxy, hydroxy, thiol, polyalkyleneoxide, polyalkylenimine, COOH, carboxylate, SO₃H, sulfonate, NE⁷E⁸,NE⁷E⁸E⁹⁺X⁻, halogen, nitro, acyl, acyloxy and cyano, where E⁷, E⁸ and E⁹are identical or different radicals selected from among hydrogen, alkyl,cycloalkyl and aryl and X⁻ is an anion equivalent,

where the alkyl radicals may bear 1, 2, 3, 4, 5 or more substituentsselected from among cycloalkyl, heterocycloalkyl, aryl, hetaryl, alkoxy,cycloalkoxy, heterx cycloalkoxy, aryloxy, hetaryloxy, hydroxy, thiol,polyalkylene oxide, polyalkylenimine, COOH, carboxylate, SO₃H,sulfonate, NE¹⁰E¹¹, NE¹⁰E¹¹E¹²⁺X⁻, halogen, nitro, acyl, acyloxy andcyano, where E¹⁰, E¹¹ and E¹² are identical or different radicalsselected from among hydrogen, alkyl, cycloalkyl and aryl and X⁻ is ananion equivalent,

and the cycloalkyl, heterocycloalkyl, aryl and hetaryl radicals R^(α),R^(β), R^(γ) and R^(δ) each bear 1, 2, 3, 4, 5 or more substituentsselected from among alkyl and the substituents mentioned above for thealkyl radicals R^(α), R^(β), R^(γ) and R^(δ), or

two or more of the radicals R^(α), R^(β), R^(γ) and R^(δ) together withthe C—C double bond to which they are bound form a monocyclic orpolycyclic compound.

Suitable prochiral olefins are olefins which have at least 4 carbonatoms and terminal or internal double bonds and have a linear, branchedor cyclic structure.

Suitable α-olefins are, for example 1-butene, 1-pentene, 1-hexene,1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene,1-octadecene etc.

Preferred linear (straight-chain) internal olefins are C₄-C₂₀-olefinssuch as 2-butene, 2-pentene, 2-hexene, 3-hexene, 2-heptene, 3-heptene,2-octene, 3-octene, 4-octene etc.

Preferred branched, internal olefins are C₄-C₂₀-olefins such as2-methyl-2-butene, 2-methyl-2-pentene, 3-methyl-2-pentene, branched,internal heptene mixtures, branched, internal octene mixtures, branched,internal nonene mixtures, branched, internal decene mixtures, branched,internal undecene mixtures, branched, internal dodecene mixtures, etc.

Further olefins suitable for the hydroformylation process areC₅-C₈-cycloalkenes such as cyclopentene, cyclohexene, cycloheptene,cyclooctene and their derivatives, e.g. their C₁-C₂₀-alkyl derivativeshaving from 1 to 5 alkyl substituents.

Olefins suitable for the hydroformylation process additionally includevinylaromatics such as styrene, α-methylstyrene, 4-isobutylstyrene,etc., 2-vinyl-6-methoxynaphthalene, 3-ethenylphenyl phenyl ketone,4-ethenylphenyl 2-thienyl ketone, 4-ethenyl-2-fluorobiphenyl,4-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)styrene,2-ethenyl-5-benzoylthiophene, 3-ethenylphenyl phenyl ether,propenylbenzene, 2-propenylphenol, isobutyl4-propenylbenzene, phenylvinyl ether and cyclic enamides, e.g 2,3-dihydro-1,4-oxazines such as2,3-dihydro4-tert-butoxycarbonyl-1,4-oxazine. Further olefins suitablefor the hydroformylation process are α,β-ethylenically unsaturatedmonocarboxylic and/or dicarboxylic acids, their esters, monoesters andamides, e.g. acrylic acid, methacrylic acid, maleic acid, fumaric acid,crotonic acid, itaconic acid, methyl 3-pentenoate, methyl 4-pentenoate,methyl oleate, methyl acrylate, methyl methacrylate, unsaturatednitriles such as 3-pentenenitrile, 4-pentenenitrile, acrylonitrile,vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl propylether, etc., vinyl chloride, allyl chloride, C₃-C₂₀-alkenols,-alkenediols and -alkadienols, e.g. allyl alcohol, hex-1-en4-ol,oct-1-en4-ol, 2,7-octadien-1-ol. Further suitable substrates are dienesor polyenes having isolated or conjugated double bonds. These include,for example, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene,1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene,1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene,1,13-tetradecadiene, vinylcyclohexene, dicyclopentadiene,1,5,9-cyclooctatriene and also homopolymers and copolymers of butadiene.

Further prochiral ethylenically unsaturated compounds which areimportant as synthetic building blocks are, for example,p-isobutylstyrene, 2-vinyl-6-methoxynaphthalene, 3-ethenylphenyl phenylketone, 4-ethenylphenyl 2-thienyl ketone, 4-ethenyl-2-fluorobiphenyl,4-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)styrene,2-ethenyl-5-benzoylthiophene, 3-ethenylphenyl phenyl ether,propenylbenzene, 2-propenylphenol, isobutyl4-propenylbenzene, phenylvinyl ether and cyclic enamides, e.g. 2,3-dihydro-1,4-oxazines such as2,3-dihydro4-tert-butoxycarbonyl-1,4-oxazine. The abovementioned olefinscan be used individually or in the form of mixtures.

In a preferred embodiment, the chiral catalysts of the invention andthose used according to the invention are prepared in situ in thereactor used for the reaction. However, if desired, the catalysts of theinvention can also be prepared separately and isolated by customarymethods. To prepare the catalysts of the invention in situ, it ispossible to react, for example, at least one ligand used according tothe invention, a compound or complex of a transition metal, ifappropriate at least one further additional ligand and, if appropriate,an activating agent in an inert solvent under the conditions of therespective reaction (e.g. under hydroformylation conditions,hydrocyanation conditions, etc.). Suitable activating agents are, forexample, Bronsted acids, Lewis acids such as BF₃, AlCl₃, ZnCl₂, andLewis bases.

Suitable catalyst precursors are transition metals, transition metalcompounds and transition metal complexes quite generally.

Suitable rhodium compounds or complexes are, for example, rhodium(II)and rhodium(III) salts such as rhodium(III) chloride, rhodium(III)nitrate, rhodium(III) sulfate, potassium rhodium sulfate, rhodium(II) orrhodium(III) carboxylate, rhodium(III) and rhodium(III) acetate,rhodium(III) oxide, salts of rhodic(III) acid, trisammoniumhexachlororhodate(III), etc. Also suitable are rhodium complexes such asRh₄(CO)₁₂, dicarbonylrhodium acetylacetonate,acetylacetonatobisethylenerhodium(I), etc.

Likewise suitable are ruthenium salts or compounds. Suitable rutheniumsalts are, for example, ruthenium(III) chloride, ruthenium(IV),ruthenium(VI) or ruthenium(VIII) oxide, alkali metal salts of rutheniumoxo acids such as K₂RuO₄ or KRuO₄ or complexes such as RuHCl(CO)(PPh₃)₃,(Ru(p-cymene)Cl)₂, (Ru(benzene)Cl)₂, (COD)Ru(methallyl)₂, Ru(acac)₃. Itis also possible to use the carbonyls of ruthenium such asdodecacarbonyltriruthenium or octadecacarbonylhexaruthenium, or mixedforms in which CO is partly replaced by ligands of the formula PR₃, e.g.Ru(CO)₃(PPh₃)₂, in the process of the invention.

Suitable iron compounds are, for example, iron(III) acetate andiron(III) nitrate and also the carbonyl complexes of iron.

Suitable nickel compounds are nickel fluoride and nickel sulfate. Anickel complex suitable for preparing a nickel catalyst is, for example,bis(1,5-cyclooctadiene)nickel(0).

Also suitable are carbonyl complexes of iridium and osmium, osmiumhalides, osmium octoate, palladium hydrides and halides, platinic acid,iridium sulfate, etc.

The abovementioned and further suitable transition metal compounds andcomplexes are known in principle and are adequately described in theliterature or they can be prepared by a person skilled in the art usingmethods analogous to those for preparing the known compounds.

In general, the metal concentration in the reaction medium is in a rangefrom about 1 to 10 000 ppm. The molar ratio of monopnicogen ligand totransition metal is generally in a range from about 0.5:1 to 1000:1,preferably from 1:1 to 500:1.

The use of supported catalysts is also useful. For this purpose, theabove-described catalysts can be immobilized in an appropriate way, e.g.by binding via functional groups suitable as anchor groups, adsorption,grafting, etc., on a suitable support, e.g. glass, silica gel, syntheticresins, polymers, etc. They are then also suitable for use as solidstate catalysts.

In a first preferred embodiment, the process of the invention is ahydrogenation (1,2-H,H-addition). In this case, a prochiral compoundcomprising at least one ethylenically unsaturated double bond is reactedwith hydrogen in the presence of a chiral catalyst as described above toform corresponding chiral compounds having a single bond. Prochiralolefins give chiral carbon-comprising compounds, prochiral ketones givechiral alcohols and prochiral imines give chiral amines.

In a further preferred embodiment the process of the invention is areaction with carbon monoxide and hydrogen, hereinafter referred to ashydroformylation.

The hydroformylation can be carried out in the presence of one of theabovementioned solvents.

The molar ratio of mono(pseudo)pnicogen ligand to the metal oftransition group VIII is generally in a range from about 1:1 to 1000:1,preferably from 2:1 to 500:1.

Preference is given to a process in which the hydroformylation catalystis prepared in situ by reacting at least one ligand which can be usedaccording to the invention, a compound or a complex of a transitionmetal and, if appropriate, an activating agent in an inert solvent underthe hydroformylation conditions.

The transition metal is preferably a metal of transition group VIII ofthe Periodic Table of the Elements, particularly preferably cobalt,ruthenium, iridium, rhodium or palladium. Particular preference is givento using rhodium.

The composition of the synthesis gas comprising carbon monoxide andhydrogen which is used in the process of the invention can vary withinwide limits. The molar ratio of carbon monoxide to hydrogen is generallyfrom about 5:95 to 70:30, preferably from about 40:60 to 60:40.Particular preference is given to using a molar ratio of carbon monoxideto hydrogen in the region of about 1:1.

The temperature in the hydroformylation reaction is generally in a rangefrom about 20 to 180° C., preferably from about 50 to 150° C. Thepressure is generally in a range from about 1 to 700 bar, preferablyfrom 1 to 600 bar, in particular from 1 to 300 bar. The reactionpressure can be varied as a function of the activity of the novelhydroformylation catalyst used. In general, the novel catalysts based onphosphorus-comprising compounds permit a reaction in a low-pressurerange, for instance in the range from 1 to 100 bar.

The hydroformylation catalysts used according to the invention and thoseof the invention can be separated from the product from thehydroformylation reaction by customary methods known to those skilled inthe art and can generally be reused for the hydroformylation.

Asymmetric hydroformylation by the process of the invention proceedswith a high stereoselectivity. Advantageously, the catalysts of theinvention and those used according to the invention generally alsodisplay a high regioselectivity. Furthermore, the catalysts generallyhave a high stability under the hydroformylation conditions, so thatlonger catalyst operating lives can generally be achieved when usingthem than when using catalysts based on conventional chelating ligandsknown from the prior art. Advantageously, the catalysts of the inventionand those used according to the invention also display a high activity,so that the respective aldehydes or alcohols are generally obtained ingood yields.

A further important 1-hydro-2-carbo addition is the reaction withhydrogen cyanide, hereinafter referred to as hydrocyanation.

The catalysts used for hydrocyanation also comprise complexes of a metalof transition group VIII, in particular cobalt, nickel, ruthenium,rhodium, palladium, platinum, preferably nickel, palladium or platinumand very particularly preferably nickel. The preparation of the metalcomplexes can be carried out as described above. These same applies tothe in situ preparation of the hydrocyanation catalysts of theinvention. Hydrocyanation processes are described in J. March, AdvancedOrganic Chemistry, 4^(th) edition, pp. 811-812, which is herebyincorporated by reference.

In a further preferred embodiment, the 1-hydro-2-carbo addition is areaction with carbon monoxide and at least one compound having anucleophilic group, hereinafter referred to as carbonylation.

The carbonylation catalysts, too, comprise complexes of a metal oftransition group VIII, preferably nickel, cobalt, iron, ruthenium,rhodium or palladium, in particular palladium. The preparation of themetal complexes can be carried out as described above. The same appliesto the in situ preparation of the carbonylation catalysts of theinvention.

The compounds having a nucleophilic group are preferably selected fromamong water, alcohols, thiols, carboxylic esters, primary and secondaryamines.

A preferred carbonylation reaction is the conversion of olefins intocarboxylic acids by means of carbon monoxide and water(hydrocarboxylation).

The carbonylation can be carried out in the presence of activatingagents. Suitable activating agents are, for example, Brönsted acids,Lewis acids, e.g. BF₃, AlCl₃, ZnCl₂, and Lewis bases.

A further important 1,2-addition is hydroacylation. In asymmetricintramolecular hydroacylation, unsaturated aldehydes are converted intooptically active cyclic ketones. In the case of asymmetricintermolecular hydroacylation, a prochiral olefin is reacted with anacyl halide in the presence of a chiral catalyst as described above toform a chiral ketone. Suitable hydroacylation processes are described inJ. March, Advanced Organic Chemistry, 4^(th) edition, p. 811, which ishereby incorporated by reference.

A further important 1,2-addition is hydroamidation. Here, a prochiralcompound comprising at least one ethylenically unsaturated double bondis reacted with carbon monoxide and ammonia or a primary or secondaryamine in the presence of a chiral catalyst as described above to form achiral amide.

A further important 1,2-addition is hydroesterification. Here, aprochiral compound comprising at least one ethylenically unsaturateddouble bond is reacted with carbon monoxide and an alcohol in thepresence of a chiral catalyst as described above to form a chiral ester.

A further important 1,2-addition is hydroboration. Here, a prochiralcompound comprising at least one ethylenically unsaturated double bondis reacted with borane or a source of borane in the presence of a chiralcatalyst as described above to form a chiral trialkylborane which can beoxidized to a primary alcohol (e.g. using NaOH/H₂O₂) or to a carboxylicacid. Suitable hydroboration processes are described in J. March,Advanced Organic Chemistry, 4^(th) edition, pp. 783-789, which is herebyincorporated by reference.

A further important 1,2-addition is hydrosilylation. Here, a prochiralcompound comprising at least one ethylenically unsaturated double bondis reacted with a silane in the presence of a chiral catalyst asdescribed above to form a chiral compound functionalized with silylgroups. Prochiral olefins result in chiral alkanes functionalized withsilyl groups. Prochiral ketones result in chiral silyl ethers oralcohols. In the hydrosilylation catalysts, the transition metal ispreferably selected from among Pt, Pd, Rh, Ru and Ir. Here, it can beadvantageous to use combinations or mixtures of one of theabovementioned catalysts with further catalysts. Suitable additionalcatalysts include, for example, platinum in finely divided form(“platinum black”), platinum chloride and platinum complexes such ashexachloroplatinic acid or divinyldisiloxane-platinum complexes, e.g.tetramethyldivinyldisiloxane-platinum complexes. Suitable rhodiumcatalysts are, for example, RhCl(P(C₆H₅)₃)₃ and RhCl₃. Also suitable areRuCl₃ and IrCl₃. Further suitable catalysts are Lewis acids such asAlCl₃ or TiCl₄ and also peroxides.

Suitable silanes are, for example, halogenated silanes such astrichlorosilane, methyldichlorosilane, dimethylchlorosilane andtrimethylsiloxydichlorosilane; alkoxysilanes such as trimethoxysilane,triethoxysilane, methyidimethoxysilane, phenyidimethoxysilane,1,3,3,5,5,7,7-heptamethyl-1,1-dimethoxytetrasiloxane and alsoacyloxysilanes.

The reaction temperature in the silylation is preferably in a range from0 to 140° C., particularly preferably from 40 to 120° C. The reaction isusually carried out under atmospheric pressure, but can also be carriedout at superatmospheric pressures, e.g. in the range from about 1.5 to20 bar, or subatmospheric pressures, e.g. from 200 to 600 mbar.

The reaction can be carried out without solvent or in the presence of asuitable solvent. Preferred solvents are, for example, toluene,tetrahydrofuran and chloroform.

A further important 1,2-addition is aminolysis (hydroamination). Here, aprochiral compound comprising at least one ethylenically unsaturateddouble bond is reacted with ammonia or a primary or secondary amine inthe presence of a chiral catalyst as described above to form a chiralprimary, secondary or tertiary amine. Suitable hydroamination processesare described in J. March, Advanced Organic Chemistry, 4^(th) edition,pp. 768-770, which is hereby incorporated by reference.

A further important 1,2-addition is alcoholysis (hydro-alkoxy-addition).Here, a prochiral compound comprising at least one ethylenicallyunsaturated double bond is reacted with an alcohol in the presence of achiral catalyst as described above to form a chiral ether. Suitablealcoholysis processes are described in J. March, Advanced OrganicChemistry, 4^(th) edition, pp. 763-764, which is hereby incorporated byreference.

A further important reaction is isomerization. Here, a prochiralcompound comprising at least one ethylenically unsaturated double bondis converted in the presence of a chiral catalyst as described aboveinto a chiral compound.

A further important reaction is cyclopropanation. Here, a prochiralcompound comprising at least one ethylenically unsaturated double bondis reacted with a diazo compound in the presence of a chiral catalyst asdescribed above to form a chiral cyclopropane.

A further important reaction is metathesis. Here, a prochiral compoundcomprising at least one ethylenically unsaturated double bond is reactedwith a further olefin in the presence of a chiral catalyst as describedabove to form a chiral hydrocarbon.

A further important reaction is aldol condensation. Here, a prochiralketone or aldehyde is reacted with a silylenol ether in the presence ofa chiral catalyst as described above to form a chiral aldol.

A further important reaction is allylic alkylation. Here, a prochiralketone or aldehyde is reacted with an allylic alkylating agent in thepresence of a chiral catalyst as described above to form a chiralhydrocarbon.

A further important reaction is [4+2]-cycloaddition. Here, a diene isreacted with a dienophile, with at least one of these compounds beingprochiral, in the presence of a chiral catalyst as described above toform a chiral cyclohexene compound.

The invention further provides for the use of catalysts comprising atleast one complex of a metal of transition group VIII with at least oneligand as described above for hydroformylation, hydrocyanation,carbonylation, hydroacylation, hydroamidation, hydroesterification,hydrosilylation, hydroboration, hydrogenation, aminolysis, alcoholysis,isomerization, metathesis, cyclopropanation or [4+2]-cycloaddition.

The process of the invention is suitable for preparing many usefuloptically active compounds. The process stereoselectively generates achiral center. Examples of optically active compounds which can beprepared by the process of the invention are substituted andunsubstituted alcohols or phenols, amines, amides, esters, carboxylicacids or anhydrides, ketones, olefins, aldehydes, nitriles andhydrocarbons. Optically active aldehydes which are preferably preparedby the asymmetric hydroformylation process of the invention comprise,for example, S-2-(p-isobutylphenyl)propionaldehyde,S-2-(6-methoxynaphthyl)propionaldehyde,S-2-(3-benzoylphenyl)propionaldehyde,S-2-(p-thienoylphenyl)propionaldehyde,S-2-(3-fluoro-4-phenyl)phenylpropionaldehyde,S-2-[4-(1,3-dihydro-I-oxo-2H-isoindol-2-yl)phenyl]propionaldehyde,S-2-(2-methylacetaldehyde)-5-benzoylthiophene, etc. Further opticallyactive compounds which can be prepared by the process of the invention(including possible formation of a derivative) are described inKirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, 1984,and The Merck Index, An Encyclopedia of Chemicals, Drugs andBiologicals, Eleventh Edition, 1989, which are hereby incorporated byreference.

The process of the invention makes it possible to prepare opticallyactive products with high enantioselectivity and, if necessary,regioselectivity, e.g. in hydroformylation. Enantiomeric excesses (ee)of at least 50%, preferably at least 75% and particularly preferably atleast 90% can be achieved.

The products obtained are isolated by customary methods known to thoseskilled in the art. These include, for example, solvent extraction,crystallization, distillation, evaporation, e.g. in a wiped filmevaporator or falling film evaporator, etc.

The optically active compounds obtained by the process of the inventioncan be subjected to one or more subsequent reaction(s). Such processesare known to those skilled in the art. They include, for example, theesterification of alcohols, the oxidation of alcohols to aldehydes,N-alkylation of amides, addition of aldehyde onto amides, nitrilereduction, acylation of ketones with esters, acylation of amines, etc.For example, optically active aldehydes obtained by asymmetrichydroformylation according to the invention can be subjected tooxidation to form carboxylic acids, reduction to form alcohols, aldolcondensation to form α,β-unsaturated compounds, reductive amination toform amines, amination to form imines, etc.

A preferred derivative-forming reaction comprises oxidation of analdehyde prepared by the asymmetric hydroformylation process of theinvention to form the corresponding optically active carboxylic acid.Many pharmaceutically important compounds such as S-ibuprofen,S-naproxen, S-ketoprofen, S-suprofen, S-fluorobiprofen, S-indoprofen,S-tiaprofenic acid, etc, can be prepared in this way.

Olefin starting materials, aldehyde intermediates and end products arelisted in the following table for some preferred derivative-formingreactions:

Olefin Aldehyde Product p-IsobutylstyreneS-2-(p-Isobutylphenyl)propionaldehyde S-Ibuprofen2-Vinyl-6-methoxynaphthalene S-2-(6-Methoxynaphthyl)propionaldehydeS-Naproxen 3-Ethenylphenyl phenyl ketoneS-2-(3-Benzoylphenyl)propionaldehyde S-Ketoprofen 4-Ethenylphenyl2-thienyl ketone S-2-(p-Thienoylphenyl)propionaldehyde S-Suprofen4-Ethenyl-2-fluorobiphenyl S-2-(3-Fluoro-4-phenyl)phenylpropionaldehydeS-Fluorobiprofen 1,3-Dihydro-1-oxo-2H-isoindol- S-2-(4-(1,3-Dihydro1-oxo-2H-isoindol- S-Indoprofen 2-yl)styrene2-yl)phenyl)-propionaldehyde 2-Ethenyl-5-benzoylthiopheneS-2-(2-Methylacetaldehyd)-5-benzoylthiophene S-Tiaprofenic acid3-Ethenylphenyl phenyl ether S-2-(3-Phenoxy)propionaldehyde S-FenoprofenPropenylbenzene S-2-Phenylbutyraldehyde S-Phenetamide, S-ButetamateIsobutyl-4-propenylbenzene S-2-(4-Isobutylphenyl)butyraldehydeS-Butibufen Phenyl vinyl ether S-2-Phenoxypropionaldehyde PheneticillinVinyl chloride S-2-Chloropropionaldehyde S-2-Chloropropionic acid2-Vinyl-6-methoxynaphthalene S-2-(6-Methoxynaphthyl)propionaldehydeS-Naproxol 2-Vinyl-6-methoxynaphthaleneS-2-(6-Methoxynaphthyl)propionaldehyde S-Naproxen (Na salt)5-(4-Hydroxy)benzoyl-3H-pyrrolizine 5-(4-Hydroxy)benzoyl-1-formyl-2,3-Ketorolac or derivatives dihydropyrrolizine tert-Butyl2,3-dihydro[1,4]oxazine- tert-Butyl 3-formylmorpholine-4-carboxylatetert-Butyl 3-hydroxymethylmorpholine- 4-carboxylate 4-carboxylate2,3-Dihydro[1,4]oxazine-4-carbaldehyde Morpholine-3,4-dicarbaldehyde3-Hydroxymethylmorpholine-4-carbaldehyde 1-Phenylvinyl acetate1-phenylvinyl acetate 3-Methylamino-1-phenylpropyl acetate

EXAMPLES Example 1 Preparation of6-(1-naphthylphenylphosphino)-2-pivaloylaminopyridine (6-NPPAP)

n-Butyllithium (8.7 ml, 14.0 mmol, 1.6 M solution in hexane, 2 eq) wasadded to a solution of 2-bromo-6-N-pivaloylaminopyridine (1.80 g, 7.0mmol) in tetrahydrofuran (30 ml) at −100° C. over a period of 20 minutesand the reaction solution was stirred at this temperature for 1 hour.After addition of chloro(1-naphthyl)phenylphosphine (1.89 g, 7.0 mmol, 1eq, prepared as described by G. Wittig et al., in Justus Liebig Ann.Chem. 1971, 17-26), the reaction solution was warmed to room temperatureover a period of 12 hours. The reaction was stopped by addition ofsaturated NaHCO₃ solution (30 ml), the, aqueous phase was separated offand extracted with ethyl acetate (3×20 ml). The combined organic phaseswere dried over MgSO₄ and the solvent was removed on a rotaryevaporator. The crude product was purified by column chromatographyusing silica gel as stationary phase and a cyclohexane/ethyl acetatemixture (10:1).

The title compound (1.50 g, 3.6 mmol, 52%) could be isolated in the formof a white solid.

Mp: 55° C.

¹H-NMR (499.873 MHz, C₆D₆): δ=0.86 (s, 9H, CH₃), 6.66 (d, J=7.5 Hz, 1H,H5), 6.93 (td, J=7.5 Hz, J=1.9 Hz, 1H, H4), 7.04-7.05 (m, 3H, Ar—H),7.11 (t, J=7.7 Hz, 1H, Ar—H), 7.17-7.19 (m, 2H, Ar—H), 7.27-7.30 (m, 1H,Ar—H), 7.43-7.47 (m, 2H, Ar—H), 7.57-7.60 (m, 2H, Ar—H), 7.92 (br, 1H,NH), 8.51 (d, J=7.5 Hz, 1H, H3), 8.75-8.77 (m, 1H, Ar—H).

¹³C-NMR (125.709 MHz, C₆D₆): δ=27.1 (s, 3C, C(CH₃)₃), 39.5 (s, 1C,C(CH₃)₃), 112.8 (s, 1C, C3), 124.5 (d, J_(C,P)=11.8 Hz, 1C, C5), 126.0(d, J_(C,P)=1.8 Hz, 1C, Ar—C), 126.4 (d, J_(C,P)=1.5 Hz, 1C, Ar—C),126.6 (s, 1C, Ar—C), 126.7 (d, J_(C,P)=18.1 Hz, 1C, Ar—C), 128.9 (d,J_(C,P)=7.3 Hz, 2C, C3″), 129.0 (s, 1C, Ar—C), 129.3 (s, 1C, Ar—C),130.0 (s, 1C, Ar—C), 132.9 (d, J_(C,P)=1.2 Hz, 1.2Hz, 1C, C4), 134.0 (d,J_(C,P)=4.2 Hz, 1C, C9′), 134.4 (d, J_(C,P)=15.1 Hz, 1C, C1′ or C1″),135.1 (d, J_(C,P)=20.6 Hz, 2C, C2″), 136.0 (d, J_(C,P)=10.9 Hz, 1C, C1′or C1″), 136.33 (d, J_(C,P)=22.1 Hz, 1C, C10′), 138.2 (d, J_(C,P)=1.5Hz, 1C, Ar—C), 152.8 (d, J_(C,P)=15.1 Hz, 1C, C2 or C6), 161.9 (d,J_(C,P)=6.4 Hz, 1C, C2 or C6), 176.5 (s, 1C, C═O).

³¹P-NMR (121.468 MHz, CDCl₃): δ=−13.72 (s)

Chiral HPLC (AD-H, n-heptane/EtOH 70:30, RT, 0.8 ml/min, 295 nm, RT)(−)-enantiomer: 5.7 min [α]_(D) = −38° (c = 0.30, CHCl₃, 21° C.)(+)-enantiomer: 6.8 min [α]_(D) = +37° (c = 0.52, CHCl₃, 21° C.)

The resolution of 200 mg of rac-6-NPPAP was carried out by means ofpreparative HPLC (Chiralpak AD-H, n-heptane/EtOH 70:30, RT, 11.0 m/min,295 nm), with the individual enantiomers being obtained in a purity ofee >99%.

Example 2 Preparation of a Heterodimeric Pt Complex

A solution of 3-diphenylphosphino-2H-isoquinolin-1-one (3-DPICone) (12.6mg, 3.82×10⁻² mmol, 1 eq) and 6-NPPAP from example 1 (14.4 mg, 3.28×10²mmol, 1 eq) in CDCl₃ (0.4 ml) was added to a solution ofPtCl₂(1,5-cyclooctadiene) (14.3 mg, 3.82×10⁻² mmol, 1 eq) in CDCl₃ (0.4ml). The formation of the heteroleptic complex was observed by means oflow-temperature NMR spectroscopy.

³¹P-NMR 294K (121.468 MHz, CDCl₃): δ=6.36 (bd, ¹J_(Pt-P)=3521 Hz), 8.02(bd, ¹J_(Pt-P)=3756 Hz).

¹H-NMR 240K (499.873 MHz, CDCl₃): δ=1.11 (s, 9H, CH₃), 6.69-6.74 (m, 2H,Ar—H), 6.88 (t, J=7.2 Hz, 1H, Ar—H), 7.17-7.27 (m, 7H, Ar—H), 7.34-7.48(m, 5H, Ar—H), 7.55-7.72 (m, 6H, Ar—H), 7.79 (d, J=8.0 Hz, 1 H), 7.81(d, J=7.9 Hz, 1H), 7.87-7.89 (br, 1H, Ar—H), 7.98 (d, J=7.7 Hz, 1H),8.04-8.08 (m, 3H, Ar—H), 8.24 (t, J=8.4 Hz, 2H, Ar—H), 10.44 (s, 1H,NH), 11.53 (d, J=5.8 Hz, NH).

³¹P-NMR 240K (121.468 MHz, CDCl₃,): δ=6.36 (dd, ¹J_(Pt-P)=3515 Hz,²J_(P-P)=13.2 Hz), 7.26 (dd, ¹J_(P-P)=3753 Hz, ²J_(P-P)=13.2 Hz).

Example 3 Asymmetric hydrogenation of methyl 2-acetamidoacrylate

A mixture of [Rh(COD)₂]BF₄ (2 mg, 5.0×10⁻³ mmol, 1.0 mol %), 3-DPICone(2.1 mg, 6.4×10⁻³ mmol, 1.3 mol %) and (+)-6-NPPAP from example 1 (2.7mg, 6.5×10⁻³ mmol, 1.3 mol %) was dissolved in dry and degassed CH₂Cl₂(5 ml) and stirred at room temperature for 10 minutes. The catalystsolution was admixed with methyl 2-acetamidoacrylate (71.6 mg, 0.5 mmol)and the solution was transferred to a steel autoclave. The autoclave wasflushed five times with hydrogen and subsequently brought to a pressureof 5 bar at room temperature for 48 hours.

After the reaction was complete, the conversion was determined by meansof ¹H-NMR spectroscopy and the enantiomeric excess was determined bymeans of chiral GC (Hydrodex β-TBDAc).

The conversion was quantitative, and the enantiomeric excess was 43%(R).

Example 4 Preparation of a Chiral Phosphonite Derivative of 6-DPPAP a)Synthesis of 6-(bis(diethylamino)phosphino)-2-pivaloylaminopyridine

2-Bromo-6-N-pivaloylaminopyridine (1.98 g, 7.7 mmol, 1 eq) was dissolvedin tetrahydrofuran (50 ml). At −100° C., n-butyllithium (10.0 ml, 1.54 Min hexane, 15.4 mmol, 2 eq) was slowly added dropwise. The yellowsolution was stirred at −100° C. for 90 minutes.Bis(diethylamino)chlorophosphane, prepared as described by J. Sakai, W.B. Schweizer, D. Seebach in Helv. Chim. Acta 1993, 76, 2654-2665 (1.62g, 7.7 mmol, 1 eq), was then added quickly. The reaction mixture wassubsequently warmed to room temperature overnight. The solvent was takenoff under reduced pressure, the residue was taken up in diethyl ether(30 ml) and admixed with degassed water (0.14 g, 0.14 ml, 7.8 mmol, 1eq). The suspension formed was filtered through Celite and magnesiumsulfate under a protective gas atmosphere. The solvent was removed atreduced pressure. The crude product was purified by means of bulb tubedistillation at 200° C. (10⁻³ mbar). The title compound was obtained asa viscous, colorless liquid (1.41 g, 4.0 mmol, 52%).

¹H-NMR (300.064 MHz, C₆D₆): δ=1.05 (s, 9H, C(CH)₃), 1.10 (t, 12H, J=7.0Hz, CH₂CH₃), 3.07 (m, 8H, CH₂CH₃), 7.25 (d, 2H, J=3.1 Hz, Ar—H), 8.01(b, 1H, NH), 8.48 (dd, 1H, J=5.0 Hz, J=4.0 Hz, Ar—H).

¹³C-NMR (100.620 MHz, C₆D₆): δ=14.9 (s, 3C, C(CH)₃), 27.3 (s, 4C,CH₂CH₃), 39.6 (s, 1C, C(CH)₃), 43.9 (d, 4C, J_(P,C)=17.4 Hz, CH₂CH₃),111.6 (d, 1C, J_(P,C)=2.9 Hz, Ar—CH), 122.8 (d, 1C, J_(P,C)=21.8 Hz,C5), 137.6 (s, 1C, Ar—CH), 152.4 (d, 1C, J_(P,C)=7.3 Hz, Ar—C), 164.8(d, 1C, J_(P,C)=13.1 Hz, Ar—C), 176.1 (s, 1C, C═O).

³¹P-NMR (121.468 MHz, C₆D₆): δ=94.3 (s)

b) Synthesis of6-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yl)-2-pivaloylaminopyridine

N-(6-(bis(diethylamino)phosphino)pyridin-2-yl)pivalamide (0.292 g, 0.60mmol, 1 eq) was dissolved in toluene (12 ml). (S)-BINOL (0.172 g, 0.60mmol, 1 eq) was subsequently added and the reaction mixture was refluxedfor 3 hours. The solvent was removed under reduced pressure. The titlecompound could be obtained in the form of a white solid (0.276 g, 0.56mmol, 93%).

¹H-NMR (300.064 MHz, CDCl₃): δ=1.37 (s, 9H, C(CH)₃), 6.71 (d, 1H, J=8.8Hz, Ar—H), 6.98 (d, 1H, J=7.5 Hz, Ar—H), 7.15-7.47 (m, 7H, Ar—H), 7.62(pt, 2H, J=8.9 Hz, Ar—H), 7.83 (d, 1H, J=8.1 Hz, Ar—H), 7.96 (d, 1H,J=8.0 Hz, Ar—H), 8.04 (d, 1H, J=8.8 Hz, Ar—H), 8.16 (b, 1H, NH), 8.27(d, 1H, J=8.5 Hz, Ar—H).

³¹P-NMR (121.468 MHz, CDCl₃): δ=167.2 (s)

Example 5 Preparation of a Heterodimeric Pt Complex

A solution of 3-DPICone (8.8 mg, 2.67×10⁻² mmol, 1 eq) and aminopyridineligand (13.2 mg, 2.67×10⁻² mmol, 1 eq) in CDCl₃ (0.4 ml) was added to asolution of PtCl₂(1,5-cyclooctadiene) (10.0 mg, 2.67×10⁻² mmol, 1 eq) inCDCl₃ (0.4 ml). The formation of the heteroleptic complex was observedby means of NMR spectroscopy.

³¹P-NMR (121.468 MHz, CDCl₃): δ=17.2 (dd, ¹J_(Pt-P)=3590 Hz,²J_(P-P)=13.4 Hz), 108.0 (d, ²J_(P-P)=13.4 Hz).

1. A process for preparing chiral compounds by reacting a prochiralcompound comprising at least one ethylenically unsaturated double bondwith a substrate in the presence of a chiral catalyst comprising atleast one transition metal complex with ligands which each have apnicogen-comprising or pseudopnicogen-comprising group and at least onefunctional group capable of forming intermolecular, noncovalent bonds,with the complex comprising ligands dimerized via intermolecularnoncovalent bonds, wherein the ligands comprise at least one structuralelement of the formula I.a or I.b

or tautomers thereof, where Pn is selected from a pnicogen atom or acoordinating atom of a pseudopnicogen-comprising group, R¹, R² are each,independently of one another, alkyl, alkoxy, cycloalkyl, cycloalkoxy,heterocycloalkyl, heterocycloalkoxy, aryl, aryloxy, hetaryl orhetaryloxy or R¹ and R² together with the phosphorus atom to which theyare bound form a 4- to 8-membered heterocycle which may additionally befused with one, two or three cycloalkyl, heterocycloalkyl, aryl orhetaryl groups, where the heterocycle and, if present, the fused-ongroups may each bear, independently of one another, one, two, three orfour substituents selected from among alkyl, cycloalkyl,heterocycloalkyl, aryl, hetaryl, COOR^(c), COO⁻M⁺, SO₃R^(c), SO₃ ⁻M⁺,PO₃(R^(c))(R^(d)), (PO₃)²⁻(M⁺)₂, NE⁴E⁵, (NE⁴E⁵E⁶)⁺X⁻, OR^(e), SR^(e),(CHR^(f)(CH₂O)_(y)R^(e), (CH₂CH₂NE⁴)_(y)R^(e), halogen, nitro, acyl andcyano, where R^(c) and R^(d) are identical or different radicalsselected from among hydrogen, alkyl, cycloalkyl, aryl and hetaryl,R^(e), E⁴, E⁵, E⁶ are identical or different radicals selected fromamong hydrogen, alkyl, cycloalkyl, aryl and hetaryl, R^(f) is hydrogen,methyl or ethyl, M⁺is a cation equivalent, X⁻is an anion equivalent andy is an integer from 1 to 240, R³ is hydrogen, alkyl alkoxy, cycloalkyl,cycloalkoxy, heterocycloalkyl, heterocycloalkoxy, aryl, aryloxy, hetarylor hetaryloxy, X is a C1-C5-alkylene bridge which, depending on thenumber of bridge atoms, may have one or two double bonds and/or one,two, three or four substituents selected from among alkyl, cycloalkyl,heterocycloalkyl, aryl, hetaryl, carboxylate, sulfonate, phosphonate,NE1 E2 (E1, E2=hydrogen, alkyl, cycloalkyl, acyl or aryl), hydroxy,thiol, halogen, nitro, acyl and cyano, where the cycloalkyl, aryl andhetaryl substituents may additionally bear one, two or threesubstituents selected from among alkyl, alkoxy, halogen,trifluoromethyl, nitro, alkoxycarbonyl and cyano, and/or one or twononadjacent bridge atoms of the C1-C5-alkylene bridge X may be replacedby a heteroatom or a heteroatom-comprising group and/or the alkylenebridge X can have one or two aryl and/or hetaryl groups fused onto it,and where the fused-on aryl and hetaryl groups may each bear one, two orthree substituents selected from among alkyl, cycloalkyl, aryl, alkoxy,cycloalkoxy, aryloxy, acyl, halogen, trifluoromethyl, nitro, cyano,carboxyl, alkoxycarbonyl and NE1E2 (E1 and E2=hydrogen, alkyl,cycloalkyl, acyl or aryl), and Y is O, S or NR⁴, where R⁴ is hydrogen,alkyl cycloalkyl, heterocycloalkyl, aryl or hetaryl, where two or moreof the radicals X and R¹ to R⁴ together with the structural element ofthe formula I.a or I.b to which they are bound may form a monocyclic orpolycyclic compound.
 2. The process according to claim 1, wherein theligands contain at least one pnicogen atom selected from among N, P, Asand Sb.
 3. The process according to claim 2, wherein the ligands containat least one nitrogen atom in the form of an imine.
 4. The processaccording to claim 1 wherein the ligands contain at least one carbenecarbon atom as pseudopnicogen atom.
 5. The process according to claim 1,wherein the distance between the atoms of the pnicogen-comprising orpseudopnicogen-comprising groups of the dimerized ligands whichcoordinate to the transition metal is not more than 5 Å.
 6. The processaccording to claim 1, wherein the ligands which are dimerized viaintermolecular noncovalent bonds are selected from among ligand/ligandpairs of the formula I:

where A and B are radicals of mutually complementary functional groupsbetween which there is a noncovalent interaction, a is, depending on thevalence of the pnicogen atom or coordinating atom of thepseudopnicogen-comprising groups and the number of coordination sitesoccupied by the radical R¹, 0 or 1, where the pnicogen atom orcoordinating atom of the pseudopnicogen-comprising group can, togetherwith at least two of the radicals R¹, R² and A or B bound thereto, alsobe part of a ring system.
 7. The process according to claim 1, whereinthe pnicogen- or pseudopnicogen-comprising group is a carbene group andthe carbene group is part of a ring system of the formula I.1.

where G¹ is NR^(B) or CR^(C)R^(D), where R^(B), R^(C) and R^(D) areeach, independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, where R^(C) or R^(D) may also be onebond equivalent of a double bond, Q¹ is a divalent bridging group havingfrom 1 to 5 atoms between the flanking bonds, R^(A) is hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl, where one of the radicalsR^(A), R^(B), R^(C), R^(D) or a radical on the group Q¹ is a functionalgroup capable of forming intermolecular, noncovalent bonds or comprisessuch a group.
 8. The process according to claim 7, where the compoundsof the formula I.1 are selected from among compounds of the formulaeI.1a to I.1d

where R^(A), R^(B), R^(C), R^(E) and R^(F) are each, independently ofone another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl orhetaryl, where one of these radicals is a functional group capable offorming intermolecular, noncovalent bonds or comprises such a group. 9.The process according to claim 1, wherein the pnicogen- orpseudopnicogen-comprising group is an imine group which is part of aring system of the formula I.2

where Q² is a divalent bridging group having from 1 to 5 atoms betweenthe flanking bonds, and R^(G), R^(H) and R^(I) are each, independentlyof one another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl orhetaryl, where one of the radicals R^(G), R^(H), R^(I) or a radical onthe group Q² is a functional group capable of forming intermolecular,noncovalent bonds or comprises such a group.
 10. The process accordingto claim 9, wherein the compounds of the formula I.2 are selected fromamong cyclic imines of the formulae I.2a and I.2b

where G² is O or NR^(K), where R^(K) is hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, R^(G), R^(H), R^(I) and R^(L) areeach, independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, where one of the radicals R^(G),R^(H), R^(I), R^(K) and R^(L) is a functional group capable of formingintermolecular, noncovalent bonds or comprises such a group.
 11. Theprocess according to claim 1, wherein the pnicogen- orpseudopnicogen-comprising group is selected from among groups of theformula I.3

where Pn is N, P, As or Sb.
 12. The process according to claim 1,wherein the functional groups capable of forming intermolecularnoncovalent bonds are selected from among hydroxyl, primary, secondaryand tertiary amino, thiol, keto, thioketone, imine, carboxylic ester,carboxamide, amidine, urethane, urea, sulfoxide, sulfoximine,sulfonamide and sulfonic ester groups.
 13. The process according toclaim 1, wherein the functional groups capable of forming intermolecularnoncovalent bonds are selected from among groups which are capable oftautomerism.
 14. The process according to claim 13, wherein, in theligands I.a or I.b, R¹ and R² together with the phosphorus atom to whichthey are bound form a 5- to 8-membered heterocycle which mayadditionally be fused with one, two or three cycloalkyl,heterocycloalkyl, aryl or hetaryl groups, where the heterocycle and, ifpresent, the fused-on groups may each bear, independently of oneanother, one, two, three or four substituents selected from among alkyl,cycloalkyl, heterocycloalkyl, aryl, hetaryl, COOR^(c), COO⁻M⁺, SO₃R^(c),SO₃ ⁻M⁺, PO₃(R^(c))(R^(d)), (PO₃)²⁻(M⁺)₂, NE⁴E⁵, (NE⁴E⁵E⁶)⁺X⁻, OR^(e),SR^(e), (CHR^(f)CH₂O)_(y)R^(e), (CH₂NE⁴)_(y)R^(e), (CH₂CH₂NE⁴)_(y)R^(e),halogen, nitro, acyl and cyano, where R^(c) and R^(d) are identical ordifferent radicals selected from among alkyl, cycloalkyl, aryl andhetaryl, R^(e), E⁴, E⁵, E⁶ are identical or different radicals selectedfrom among hydrogen, alkyl, cycloalkyl, acyl, aryl and hetaryl, R^(f) ishydrogen, methyl or ethyl, M⁺is a cation equivalent, X⁻is an anionequivalent and y is an integer from 1 to
 240. 15. The process accordingto claim 14, wherein the heterocycle is chiral.
 16. The processaccording to claim 1, wherein the ligands are selected from amongcompounds of the formulae I.A to I.C

and the tautomers thereof, where one of the radicals R⁵ to R⁹ is apnicogen- or pseudopnicogen-comprising group, the radicals R⁵ to R⁹which are not a pnicogen- or pseudopnicogen-comprising group are each,independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl, hetaryl, WCOOR^(o), WCOO⁻M⁺, W(SO₃)R^(o),W(SO₃)⁻M⁺, WPO₃(R^(o))(R^(p)), W(PO₃)²⁻(M⁺)_(2,) WNE¹E²,W(NE¹E²E³)⁺X⁻WOR^(q), WSR^(q)(CHR^(r)CH₂O)_(x)R^(q), (CH₂NE¹)_(x)R^(q),(CH₂CH₂NE¹)_(x)R^(q), halogen, nitro, acyl or cyano, where W is a singlebond, a heteroatom, a heteroatom-comprising group or a divalent bridginggroup having from 1 to 20 bridge atoms, R^(o) and R^(p) are identical ordifferent radicals selected from among alkyl, cycloalkyl, aryl andhetaryl, R^(q)E¹, E², E³ are identical or different radicals selectedfrom among hydrogen, alkyl, cycloalkyl, acyl, aryl and hetaryl, R^(r) ishydrogen, methyl or ethyl, M⁺is a cation equivalent, X⁻is an anionequivalent and x is an integer from 1 to 240, where two vicinal radicalsR⁵ to R⁹ may also form a fused ring system, and R^(a) and R^(b) are eachhydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, andR^(a) can also be acyl.
 17. The process according to claim 16, whereinthe radicals R⁵to R⁹ which are a pnicogen- or pseudopnicogen-comprisinggroup are each a group of the formula —W′—PnR¹R², where W′ is a singlebond, a heteroatom, a heteroatom-comprising group or a divalent bridginggroup having from 1 to 4 bridge atoms between the flanking bonds.
 18. Aprocess for preparing chiral compounds by reacting a prochiral compoundcomprising at least one ethylenically unsaturated double bond with asubstrate in the presence of a chiral catalyst comprising at least onetransition metal complex with ligands selected from among compounds ofthe formulae I.A to I.C

and the tautomers thereof, where one of the radicals R⁵ to R⁹ is apilicogen- or pseudopnicogen-comprising group, the radicals R⁵ to R⁹which are not a pnicogen- or pseudopnicogen-comprising group are each,independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl, hetaryl, WCOOR^(o), WCOO⁻M⁺, W(SO₃)R^(o),W(SO₃)⁻M⁺, WPO₃(R^(o))(R^(p)), W(PO₃)²⁻(M⁺)_(2,) WNE¹E²,W(NE¹E²E³)⁺X⁻WOR^(q), WSR^(q), (CHR^(r)CH₂O)_(x)R^(q),(CH₂NE¹)_(x)R^(q), (CH₂CH₂NE¹)_(x)R^(q), halogen, nitro, acyl or cyano,where W is a single bond, a heteroatom, a heteroatom-comprising group ora divalent bridging group having from 1 to 20 bridge atoms, R^(o) andR^(p) are identical or different radicals selected from among alkyl,cycloalkyl, aryl and hetaryl, R^(q), E¹, E², E³ are identical ordifferent radicals selected from among hydrogen, alkyl, cycloalkyl,acyl, aryl and hetaryl, R^(r) is hydrogen, methyl or ethyl, M⁺is acation equivalent, X⁻is an anion equivalent and x is an integer from 1to 240, where two vicinal radicals R⁵ to R⁹ may also form a fused ringsystem, and R^(a) and R^(b) are each hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, and R^(a) can also be acyl.
 19. Theprocess according to claim 16, wherein the ligands are selected fromamong compounds of the formulae I.i to I.iii

and the tautomers thereof, where b is 0, or 1, and R⁶ to R⁹ are each,independently of one another, hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, aryl,heteroaryl, acyl, halogen, C₁-C₄-alkoxycarbonyl or carboxylate, wheretwo vicinal radicals R⁶ to R⁹ may also form a fused ring system, andR^(a) and R^(b) are each hydrogen, alkyl, cycloalkyl or aryl, and R^(a)can also be acyl.
 20. The process according to claim 1, wherein theprochiral compound is selected from among olefins, aldehydes, ketonenand imines.
 21. The process according to claim 1 which is ahydrogenation, hydroformylation, hydrocyanation, carbonylation,hydroacylation, hydroamidation, hydroesterification, hydrosilylation,hydroboration, amino lysis, alcoho lysis, isomerization, metathesis,cyclopropanation, aldol condensation, allylic alkylation or[4+2]-cycloaddition.
 22. The process according to claim 1 which is a1,2-addition.
 23. The process according to claim 1 which is ahydroformylation.
 24. The process according to claim 1 which is ahydrogenation.